Deep Time on the Mississippi: The River's Geologic Origins and Future with Roy Van Arsdale

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How do you tell the story of a river that's tens of millions of years in the making? In Episode 79, I sit down with Dr. Roy Van Arsdale, Professor Emeritus at the University of Memphis, to trace the deep geologic history of the Mississippi River—and it's a more dynamic ride than you might expect.

We go back 100 million years, to a time when rivers in North America generally flowed north and west, then follow the dramatic forces that reversed the continent's plumbing, including a drifting hot spot that lifted part of a mountain range nearly two miles, which then eroded and sank, creating a trough for the river we call the Mississippi. Roy talks about the pre-Ice Age river that was much bigger than today’s Mississippi (and why it carried more water) and explains how glaciers rerouted the river's course. He also describes one of his first studies where he learned how bald cypress tree rings in Reelfoot Lake still bear witness to the New Madrid earthquakes of 1811–12. We even peer into the river's future, describing how uplift that is still in progress will likely change the future Mississippi River, as well as ongoing seismic risks.

If you've ever wondered how America's greatest river came to be, this conversation is for you. Listen wherever you get your podcasts, or find show notes at MississippiValleyTraveler.com/podcast.

Episode Transcript

Dr. Roy Van Arsdale (00:00):
If you lift it and strip it, but then drop
it to where it was, youessentially have it removed and
made a trough, and that's whatthe Mississippi Embayment is.
It's a big erosional troughrelated to that uplift and then
subsidence, and with thesubsidence, the Gulf of Mexico
migrates up into the continent.
With the subsidence we now arecapturing drainage from the mid

(00:21):
continent and directing it tothe south because that trough
becomes deeper from north tosouth.

Dean Klinkenberg (00:52):
Welcome to the Mississippi Valley Traveler
podcast. I'm Dean Klinkenberg,and I've been exploring the deep
history and rich culture of thepeople and places along
America's greatest river, theMississippi, since 2007. Join me
as I go deep into the charactersand places along the river, and
occasionally wander into otherstories from the Midwest and

(01:12):
other rivers. Read the episodeshow notes, and get more
information on the Mississippiat MississippiValleyTraveler.com
Let's get going.
Welcome to episode 79 of theMississippi Valley Traveler
Podcast. In this episode today,I have a really fascinating

(01:34):
conversation with Dr. Roy VanArsdale, who is Professor
Emeritus at the University ofMemphis. I had a chance to
connect with him a few years agowhen I was working on an article
for Smithsonian Magazine aboutthe long geologic history of the
Mississippi, and Roy was areally good resource to help me
understand how the river haschanged and changed its form and

(01:58):
shape so much over time. Sonaturally I thought this would
be a great topic for thepodcast, so I invited Ron to
have a wide-ranging conversationabout the long and somewhat
complicated history of the riverwe call Mississippi. So, in this
episode, we will talk a littlebit about what North America
looked like about 100 millionyears ago.

(02:20):
So we begin with a fairly briefoverview of what North America
looked like about 100 millionyears ago. We talked a little
bit about the rivers at thattime, what their directions they
tended to flow at that point intime, and then we describe, or
he describes some of the changesthat began to take place at a

(02:43):
geologic level that shifted theflow of water on the North
American continent that wouldeventually give us the
Mississippi River.
One of the more fascinatingaspects of this is where he
describes his, his incredibleresearch that has uncovered
essentially the process, thegeologic processes that created

(03:05):
the area we call the MississippiDelta, which technically called
the Mississippi Embayment. It'sthat part of the Mississippi
River, south of Cairo, Illinoisdown to the to the Gulf. There's
a fascinating story behind howthat area came to be part of the
Mississippi River Basin.
Then we move into a discussionof how the river changed for the

(03:28):
10s of millions of years beforethe ice age, how big Mississippi
got at one point, and what weresome of the forces, the geologic
forces that created such a largeriver, and then how the massive
sheets of ice, those glacierschanged the direction and flow
of the Mississippi River.

(03:49):
And then we kind of wrap it upby talking a little bit about a
few of the questions that hethinks are still unanswered
about the geologic history ofthe Mississippi and what the
river might look like down theroad a piece, at least in
geologic terms. It's not a riverany of us alive today are likely
to see, but what are some of theforces that are continuing to

(04:10):
shape the river today and howmight that alter the future
Mississippi River?
Well, thanks to all of you whoparticipated in the Kickstarter
campaign, that is officiallyfinished now. Happy to say it
funded, and it funded above thegoal that I had initially set.
So, if you supported theKickstarter campaign in the next
couple of weeks, I will begetting the fulfillment stage,

(04:33):
so books will be going outpretty soon. I have to order
hard copies of the print and ofthe paperback and the hardcover
yet, but I'll keep you up todate on the process for that.
The digital copies will go outmuch sooner than the print
copies, obviously, probablywithin a couple weeks. So, thank
you again. I'm deeply moved bythe number of people who

(04:53):
contributed to the campaign andhelped me reach that funding
goal. I'm sure you'll be hearingmore about that book as time
goes on, because there'll be amore widespread release coming
up, probably in mid to lateAugust, when the book will
become available in the usualonline marketplaces.
Until then, I still have thePatreon going, and I'm so

(05:15):
grateful for those of you whoalso are showing some love
through Patreon. That supportkeeps this podcast rolling
along. It makes it possible. Sofor as little as $1 a month, you
can join the Patreon community,and for that, you get early
access to every episode. IfPatreon isn't your thing, buy me

(05:35):
a coffee. You can, I have afairly substantial caffeine
habit. I appreciate every littlebit that helps me stay
caffeinated and alert, so thanksto those of you who've also
occasionally dropped somesupport through the buy me a
coffee option. If you want toknow how to do either one of
those, go toMississippiValleyTraveler.com/podcast

(05:57):
and from there you'll find outhow to join the Patreon
community or how to buy me acoffee. And at that same place
you'll find a list of everysingle previous episode, all 78
previous episodes, and you canalso get to the show notes for
this one. In the in the shownotes for this episode, for
example, you'll find links ordescriptions of some of the

(06:21):
books and articles that Roymentions during our
conversation.
Well, with that, let's get onwith the interview. Dr. Roy Van
Arsdale is professor emeritus atthe University of Memphis. His

(06:44):
research has been primarily inthe geology fields of
geomorphology and structure.
While he's conducted research inUtah, Oklahoma, Tennessee,
Arkansas, Kentucky, Missouri,and Australia, much of his
research has been in theMississippi Valley, studying its
evolution and the seismichazards of the New Madrid
seismic zone. He has authored orco-authored approximately 100

(07:05):
geology articles and written twobooks. Welcome to the podcast,
Roy.

Dr. Roy Van Arsdale (07:12):
It's good to be here.

Dean Klinkenberg (07:15):
I always like to start off with just a quick
question about how you gotinterested in your field. So,
what was your path to studyinggeology?

Dr. Roy Van Arsdale (07:25):
Well, to be totally honest, I was thinking
about being a chemist, and thenI thought, you know, I really
don't want to be inside all thatmuch, so what's the closest
thing that will get me outsideand still involved chemistry and
geology, was a naturalfollow-up, plus the fact that as

(07:46):
a child I spent a lot of timehiking in the woods. I lived in
Maine for a while, down inTexas, I did a lot of hiking
around in the desert, and Ithoroughly enjoyed the outdoors.

Dean Klinkenberg (07:57):
So, what were some of the earliest projects
you got to work on when you werestudying geology or training to
be a geologist?

Dr. Roy Van Arsdale (08:04):
Well, I actually started training to be
a micro paleontologist, which isnot a small paleontologist, but
someone who studies smallfossils, and this was I was
working with Lamont-DohertyGeological Observatory, while I
was a senior at RutgersUniversity, and, and I decided,

(08:28):
after a month or two of staringinto a microscope, that I would
go insane if I had to do thatfor vocation, and so the first
real research that I gotinvolved with was at the
University of Cincinnati, whereI flipped the entire script and
ended up working in desertgeomorphology south of Phoenix,

(08:50):
where I was looking at calicheand how that affected the
landscape.

Dean Klinkenberg (08:55):
Alright, so for folks listening, that
probably have a mix of peoplewho have some science background
and some who don't, can you canjust explain basically like what
a geomorphologist studies, likewhat geomorphology is?

Dr. Roy Van Arsdale (09:10):
Yeah, it's a study of landforms and how
they develop. Such things asrivers and glaciers in the
subaerial environment, the wind,erosion, all the things that are
involved in sculpting thelandscape, and then for those
who are doing submarinegeomorphology, the processes at

(09:32):
work on the sea floor and in theoceans, but all my work has been
subaerial, continental typestuff, and so I've studied, for
example, as I said, caliche,which is a desert soil, it's
actually nature's concrete thatforms in desert soils, and also

(09:52):
I've worked on the geologicevolution of the Mississippi
River Valley and how it came tobe, which is largely a
geomorphological study. Theriver's history and
characteristics, and thelandforms of the Mississippi
Embayment with where theMississippi River flows through.

Dean Klinkenberg (10:14):
So, what led you to studying the Mississippi?
That ended up being, as I readyour, your resume, your vita, it
looks like the Mississippigeomorphology has kind of been
the focus of much of yourcareer. How did you get there?

Dr. Roy Van Arsdale (10:30):
Well, part of it is simple proximity. I
like to be able to drive to myresearch area, as opposed to
picking up and going around theworld, and then coming back and
realizing you forgot to dosomething. So it's much easier
to do work in your backyard. Ifyou make a mistake or you forgot
something, you just turn aroundand go back and get it, plus the

(10:51):
fact that as an academic, whenyou get students involved, it's
it doesn't cost as much if youstay local and work in your
backyard. Students can afford todo these types of projects on
low budgets, and plus I justfind the Mississippi River
fascinating. It probably startedas a graduate student at

(11:13):
Cincinnati. We took a field tripfrom the University of
Cincinnati to Reelfoot Lake,which is a lake that formed
during the earthquakes of 1811,1812 specifically February
earthquake of 1812. And we werebasically standing on a pier

(11:35):
overlooking the lake, and Ibecame very interested in the
bald cypress trees that were outin the lake, and wondering if
they had a story to tell. Andmany years later, as a faculty
at the University of Arkansas, Iwas able to talk a
dendrochronologist, that is aperson who studies tree rings,

(11:56):
to join me in a research projectto look at the tree rings in
Reelfoot Lake.

Dean Klinkenberg (12:03):
Wow, so what did you find out from that?

Dr. Roy Van Arsdale (12:05):
Well, it turned out to be quite a
fascinating story. The treesthat are out in the lake predate
the earthquakes, and so theylived through it, and when we
cord into these trees, weextracted the cores and saw that
there was dramatic growthincrease in 1812, 1813, 1814,

(12:32):
about a 10 year period. The ringwidth increased tenfold, what
they had been pre earthquake. Wealso saw that the wood post
earthquake was solid, and preearthquake the cores, the
individual rings were werecracked, so these trees were
severely shaken, such that theybroke and cracked. They

(12:55):
responded to the earthquakesprobably because the other trees
died. Bald cypress love water,and even though it was inundated
by about a meter of water, theysurvived the flooding, whereas
their competition didn't, and sothe bald cypress thrived in this
year-around water supply. Youcould also see, frankly, that

(13:21):
there was a difference in thetype of wood that was being put
down. I think you may be awarethat your audience is aware that
many trees put down a two ringsin the course of a year. There's
a low density light coloredspring wood, and then there's a
late summer higher density darkwood, and so when you look at

(13:44):
these tree rings, you canactually see the earthquake,
because the ring color shifts.
It goes from light, dark, light,dark of systematic pattern pre
earthquake to almost all lightpost earthquake, because there
was no late summer drought.
These trees were in water fromfirst spring to first freeze,

(14:05):
and they just gobbled it up andthrived, and for whatever reason
they resorted to their originalgrowth pattern after about 10
years, which I don't understandwhy that's the case either, but
it did happen.

Dean Klinkenberg (14:23):
You know, one of the things I love about this
is that there's so many storiesto uncover that cover these
almost unimaginable amounts oftime. At least with the period
we're talking, with the NewMadrid earthquake, and looking
at the trees, we can almost getour heads around a couple 100
years, but what we're about totransition into are much, much
larger timescales, but there'sstill some incredible stories to

(14:46):
tell about how the land changed,how the rivers changed during
that time period. So, what Ithought maybe we would start
with is if we go back in timeto, I don't know, roughly 100
million years or so ago, beforethere was any trace of the river
we call Mississippi today. Whatwas North America like at that
time? What rivers existed, andwhat was the pattern for where

(15:10):
they drained?

Dr. Roy Van Arsdale (15:12):
Okay, so 100 million years in prior that,
the area of what is now theMississippi River Valley was in
the middle of a mega continentcalled Gondwana. And so it was

(15:32):
in the middle of this giantcontinent with the mountain
range that ran right through themiddle of it, that mountain
range being what we see today asthe Appalachians, the Ouachitas,
and all the way down to theMarathons in Texas, and in fact,
100 million years ago, and priorto that, drainage off of this

(15:53):
mountain range was to the north,off of this mountain range, and
so the predecessor to theMississippi would have been a
north flowing river system.
Evidence is strong that therivers flowed north and west,
because over in western statesat this time period, actually
older than 100 million years,but still prior to 100 million

(16:17):
years, they find sediments thatcould only have come from the
Appalachians, and I'm talkingabout sediments that finally
came to rest in places likeUtah, and so the physical
evidence of the depositionalhistory in North America was
that prior to our currenttopography there was a

(16:38):
drastically differenttopography, and that there was
this through going mountainrange, which divide the
drainage, half of which wentnorth up through the United
States and on to the westernstates.

Dean Klinkenberg (16:55):
What are there any current rivers that might
have followed some of thoseolder pathways or parts or
channels of current rivers thatmight, like, for example, be
part of the ancient rivers thatflowed north?

Dr. Roy Van Arsdale (17:11):
Well, not that I'm aware of. In part
because there was a majorerosional event that happened
after these rivers formed thatbasically removed the landscape,
changed the landscape sodramatically that nothing would

(17:33):
have in the immediate area ofthe central United States,
severe erosion would haveeliminated any paleo drainage.
What we see basically is theremnant being deposits much
further to the west, and inplaces like Utah.

Dean Klinkenberg (17:51):
All right, so a few years ago, Dr. Sally
Potter McIntyre published apaper where, based on their
analysis, they were estimatingthe river, let's say that we
call Mississippi, or a riverthat would flow more southerly,
at least from in the middle ofthe continent, probably began
flowing some 70 million years orso ago. What changes were

(18:14):
happening geologically aroundthat time that might have helped
shift the flow of water on thecontinent.

Dr. Roy Van Arsdale (18:22):
Well, the work that Randy Cox and I have
conducted indicates that thereversal flow to its
contemporary southern flow isrelated to the movement of North
America over a hotspot,specifically what's called the

(18:42):
Bermuda hotspot. Now, a hotspotis a deep-seated volcano, like
that which underlies theHawaiian Islands. A different
one underlies Yellowstone. Andlet's just reflect on on Hawaii
for a moment here. As thePacific plate moves in a

(19:04):
westerly direction, this deepmagma source is stationary
relative to that western drift,and as it drifts, the volcano
becomes active again and pops ahole through the crust to the
surface, and so you end up witha dotted line across the sea
floor that literally marks thetrace of the Pacific plate over

(19:25):
top of that hotspot.
We see the same thing inYellowstone. If you start at
Yellowstone, where the modernhotspot currently lies and is
fueling volcanic activity andhot springs and geysers, you can
see where it went in the pastrelative to North America. It's
right down the Snake River Plainall the way to the coast, and

(19:48):
that's why the states ofWashington and Oregon are
covered by lava flows. Becausethe Yellowstone hotspot used to
be under Washington and Oregonas North America. America
drifted westward, and itscurrent position now underneath.
Okay, so back to the midcontinent. So, if we go back,

(20:09):
let's just say 120 million yearsago, or thereabouts, the Bermuda
hotspot, relatively speakingnow, was northwest of the
Mississippi Valley. As NorthAmerica moved westerly. That hot
spot stayed in its position, andwe just moved right over top.
And right around 100 millionyears ago the hotspots globally

(20:33):
became very active. This was notjust a unique Mississippi Valley
event; this was occurringglobally for reasons that aren't
really clear, but they were veryactive, and so when the hot spot
was directly underneath what isnow the Mississippi River
Valley, it was very active about100 million years ago, and the

(20:54):
magma was ascending, and it wascoming up, frankly, along
ancient fractures in the crust.
This goes back much further intime to, to say, 600 million
years ago the mid continent waswas cracked. In fact, the
southeastern corner of the whatis now the United States nearly

(21:17):
ripped off 600 million yearsago, but it didn't go to
completion. So there's thismajor crack that runs up through
it's called the Reelfoot Rift.
Now we are further in time, andthis hotspot happens to sit
right under this busted up rock,which allows for the ascent of
the magma to come up thesefracture planes along the fault

(21:38):
planes, and in so doing, itheats the crust, alright. The
ascent of the magma heats thecrust and makes it swell, right?
When you heat something up, itswells up, and in so doing, it
lifted the landscape andliterally formed a, an arch or a
subtle mountain that would haverun down the length of the

(22:00):
Mississippi River Valley, and itwas about three kilometers tall,
about two miles high. So, whatpreceded the Mississippi
Embayment trough was actually anarch that was driven by the heat
of that plume or hotspot thatwas pumping heat into the crust

(22:20):
and making the crust swell up.
Well, okay, so if you lift thelandscape three kilometers,
erosion just attacks it, and sothat three kilometer high welt
that was trending northeastsouthwest under what is now
pretty much the MississippiRiver underwent erosion, and

(22:44):
about three kilometers ofsediment was stripped off by
erosion. Essentially, thatmountain was eroded down to sea
level. Now this drift of NorthAmerica continues through this
whole story, and eventually itdrifts off the hotspot, so the
hotspot is now under what is bethe Appalachians, say in the

(23:05):
order of 40 million years ago.
Well, with the removal of theheat source, the that ancient
upwelt now contracts, cools, andsinks, and that which was two
kilometers above sea level,which was eroded away, is now
two kilometers below sea level.

(23:28):
I don't know if you followedthat, but if you lift it and
strip it, but then drop it towhere it was, you essentially
have a removed and made atrough, and that's what the
Mississippi Embayment is. It's abig erosional trough related to
that uplift, and thensubsidence, and with the
subsidence, the Gulf of Mexicomigrates up into the continent.

(23:50):
With the subsidence, we now arecapturing drainage from the mid
continent and directing it tothe south, because that trough
becomes deeper from north tosouth. The trough, Mississippian
Embayment, and the arch thatpreceded it extended pretty much
from southern Illinois all theway down to what is now

(24:11):
Louisiana all the way to theGulf.
One of the things that somepeople have argued is that the
Mississippian Embayment wasrelated to the opening of the
Gulf of Mexico, that is not thecase. There is about a 30
million year difference betweenthe opening of the Gulf of
Mexico and the subsequenthotspot story and hotspot

(24:32):
mechanism. They're not relatedevents. So the uplift and
subsidence is a hotspot event,not a Gulf of Mexico event. Some
people want to reactivate thatancient rift and propagate it up
to the north, causingsubsidence, but that is clearly

(24:53):
not the story. They're just notrelated events. That hotspot,
which is called the Bermudahotspot, is actually is left of
it, not much of anything is eastof the island of Bermuda. Now
it's pretty much shut down, butone of the last manifestations
of that hotspot is the island ofBermuda, of which, of course,

(25:17):
the uppermost part is covered byreefs. You don't see the volcano
until you drill about 200 feet,but it's there, and it makes up
a very large uplift of the seafloor, which is what the Bermuda
Island sits on top of.

Dean Klinkenberg (25:34):
Wow, I mean, I know you've been working on this
particular reconstruction ofgeology for quite some time. It
was a 20 some years ago youpublished an article about this
in National Geographic, or oneof those publications?

Dr. Roy Van Arsdale (25:48):
We first started the really best
publication, technically, is theI believe it was in Tectonics,
but then we published aScientific American article,
which they did a great job inproviding the graphics to

(26:08):
illustrate our points, and it'scertainly written in a much more
easily accessible manner forpeople who are not trained in
geology to read and and follow,but yes, it's probably been 20
years. I didn't realize it hadbeen that long, but yeah, it
probably has been.

Dean Klinkenberg (26:27):
Yeah, when, when you first presented this
idea to your colleagues, how wasit received?

Dr. Roy Van Arsdale (26:36):
Mixed, some people, you know, thought that
that's crazy and laughed, andthen we started to notice that
people were referencing,particularly people at Berkeley
and Stanford, and some of the,frankly, the powerhouse programs

(26:57):
jumped on this. We have since,in fact, there was an article
just published within the lastcouple months where they look
very carefully at the chemistryof some of these igneous rocks
that are actually exposed.
There's a quarry over in LittleRock where these rocks that came
from deep within the earth, fromthe mantle, are exposed in a

(27:19):
quarry, and they did chemicalanalysis, and came to the
conclusion that indeed theserocks are from deep within the
earth. It's related to ahotspot, and so the evidence is
coming in from other people whowere looking at this and have
been looking at this. We hadanother scientist contact Randy

(27:41):
and say, "Thank you for thatarticle. I've often wondered
what this is that I see over inMississippi and Alabama that I
could never explain."Apparently, it's, it's related
to the hotspot track and sitsright on what he had found as
being anomalous in in hisgeologic study. So there's been
there's been mostly positiveresponse to this. Some people

(28:06):
still don't, aren't onbandwagon, which is normal,
right?

Dean Klinkenberg (28:16):
That's normal in science. Yeah, I'm trying to
get my head around what thingsmight look like now, too. So, I,
so after the hot spot movedaway, and the rocks cooled and
sank back down, we're talking atwo kilometer trench,

(28:39):
essentially, I guess then thesediment and sand and all that
began to fill in much of that asthe river flow to drop sediment,
it began to fill in that gap. AmI on the right track so far?

Dr. Roy Van Arsdale (28:54):
That's correct, and a couple other
things I should probably pointout. There's obviously a number
of lines of evidence that wepresented in our discussion of
this, but prior to 100 millionyears ago, there were just reefs
around the Southern Gulf coast,which means there was no big

(29:16):
river, because reefs don't likerivers, and so clearly there was
no Mississippi River more than100 million years ago, because
there's no indication of of abig sand body coming into the
northern Gulf of Mexico. That'sthat's certainly one line of

(29:38):
evidence. We were also able toget a hold of radiometric dates
of igneous rocks that wereburied and drilled by oil
companies as they were exploringfor oil and gas, they bring up
rocks from the bottom of thehole and radiometrically date
them, and the ages of theseigneous rocks diminish in age

(30:00):
from northwest to southeast.
Indicating that the NorthAmerican plate was moving from
southeast to northwest, and thatthis, this hot magma source
relative to the United States,was moving in a southeasterly
direction.
There were a couple other thingsthat made this argument strong.

(30:20):
If we go back 100 million yearsago and reflect on the fact that
drainage was actually to thenorth, as we talked about
earlier, meaning that there wasa mountain range. The
Appalachians were a hugemountain range, and as were the
Ouachitas and the Marathons, youhave to breach a mountain range
to make the Mississippi RiverValley, how do you do that?

(30:42):
Well, the hotspot provides theway of doing this, that
literally the hotspot wentrelative, relatively speaking,
again underneath thatAppalachian Ouachita mountain
chain, and so what was alreadyhigh was lifted higher and
subjected to more severe erosionand deeper erosion, and then

(31:04):
when it dropped, it was threekilometers below sea level. The
deepest part of theMississippian Embayment is
actually sits on top of what wasthe Appalachian or Ouachita
mountain chain that was onecontinuous mountain range over
100 million years ago,

Dean Klinkenberg (31:20):
And how far down would we have to drill to
get to that rock now?

Dr. Roy Van Arsdale (31:23):
Three kilometers,

Dean Klinkenberg (31:24):
Three kilometers, right? Yeah.

Dr. Roy Van Arsdale (31:26):
Yeah, the deepest part is right over top
of what would be what is theremnants of the Appalachian
Mountains at three kilometersdepth that continue across our
Alabama, Mississippi, Arkansas,and on to the west.

Dean Klinkenberg (31:45):
So how, how wide is the gap now? How much of
a, so how much of a gap openedup between in the mountain
chains?

Dr. Roy Van Arsdale (31:54):
About 100 miles, about the width of the
valley. It actually kind ofdiminishes in width as you, if
you follow, look at the valleyin a map, it's a bit wider north
of where the Appalachian were,and then it opens up again once
you get across the ancientmountain chain area. So there's

(32:15):
somewhat of a manifestation ofthe effect of that previous
mountain chain, and just thewidth of the valley.

Dean Klinkenberg (32:22):
Well, just, just for clarity, too. I know we
misuse these terms sometimes,but that the area we're talking
about is what a lot of peoplecall today the Delta, which is,
you know, the part of theMississippi south of Memphis,
essentially the Delta, anyway,is that area from Memphis to
roughly Vicksburg or so, andthen east and west, about 100

(32:43):
miles, but with the area you'retalking about affected by the
hotspot is actually much largerthan that.

Dr. Roy Van Arsdale (32:49):
Much larger. All the way from
southern Illinois to off theshelf south of offshore
Louisiana.

Dean Klinkenberg (33:01):
All right, so we finally get them a route
opened for a river to go southto the Gulf, and we're still
talking 10s of millions of yearsago. The river was hardly static
during that time. So, can yougive me a little bit of sense of
like what that, when the riverbegan flowing, what do we know

(33:22):
about what kind of river it wasin the earliest few million
years? How long might it havebeen? Was it comparable in
discharge of volume to what wesee today> Do we know what? Can
we speculate about any of thosethings?

Dr. Roy Van Arsdale (33:39):
I don't really have, I, I've never
really pursued that, so I don'thave any, I don't really have
any comments to make to that.
Let me think about that for justa moment here, but we could, we
could probably back calculatethat by looking at the deposits
that were were made in thenorthern Gulf of Mexico, I'm

(34:05):
sure if we could go through oilcompany records, we could come
up with an answer for you onthat, because they've drilled
the heck out of it, and theywould know the distribution of
the sediments and how thick theyare and how extensive they are,
and then that you could prettyreadily back calculate what size
river you'd have to have toproduce that big package of

(34:25):
sediment down there, but that'snot something I've done. I've
actually made some inquiries tosee if I could get somebody
interested in doing that, andnever had any success at that,
because it does to be done well,you'd have to open up the
records of the oil companies andsee what they have, because they
would certainly be able toanswer that question if they are

(34:47):
willing to provide theinformation.

Dean Klinkenberg (34:51):
Sounds like somebody's future dissertation.

Dr. Roy Van Arsdale (34:53):
Absolutely, absolutely make a great
dissertation.

Dean Klinkenberg (34:59):
Hey, Dean Klinkenberg here interrupting
myself. Just wanted to remindyou that if you'd like to know
more about the MississippiRiver, check out my books. I
write the Mississippi ValleyTraveler guidebooks for people
who want to get to know theMississippi better. I also wrote
The Wild Mississippi, a guidethat goes deep into the complex

(35:20):
ecosystem supported by theMississippi, the plant and
animal life that depends onthem, and where you can go to
experience it all. If you likefiction, check out my Frank
Dodge mystery series. Each bookis set in places along the
Mississippi River. My newestbook is a travel memoir called

'Better Safe Than Sorry (35:37):
Slow Boats, Chicken Busses and the
Radical Choice to Trust theWorld.' The book explores a

simple question (35:45):
What happens when you stop asking what if
something goes wrong and startasking what if everything goes
right? Find out more atdeanklinkenberg.com/bettersafethansorry.
You do have some other papers,though, where you write about
characteristics of the river inthe pre-glacial time period,

(36:08):
where you've looked at oldmeander belts and kind of
estimated how much water musthave been carried by the river
at different points in time. Canyou speculate? Can you maybe
summarize a little bit aboutwhat this pre ice age river, how
it sort of grew and changedacross time, and the general
course.

Dr. Roy Van Arsdale (36:31):
Yes, we pick up the story, I say "we",
here in Memphis pick up thestory, of the Mississippi River
from ancient to relativelyrecent, about 3.6 million years
ago, in studying ancestralMississippi sediments that are

(36:52):
preserved underneath Memphis andShelby County. These sand and
gravel deposits are underneathwesternmost Kentucky, southern
Illinois, Crowley's Ridge inArkansas, and go all the way
down into Louisiana. It's ared-colored sand and gravel
deposit that is exploited as theprincipal aggregate source for

(37:14):
construction in this part of thecountry. What they're, what
they're digging up is theancient Mississippi River of 3.6
million years ago. It's locallycalled the Upland Complex. It
has different names in differentareas. It's called the Mounds
Gravel up in Illinois. And it'snot at the surface, it's varied

(37:38):
by windblown silt, what's calledloess, related to the subsequent
ice ages, but beneath this loessblanket that covers everything
out here, just about, is thisvery pronounced, approximately
10 to 20 meter thick sand andgravel unit that is the

(37:59):
ancestral Mississippi, and itextends from east of Memphis all
the way to almost to theeasternmost edge of Shelby
County to Crowley's Ridge, andprobably all the way over to
Little Rock, but it's beenremoved by erosion west of
Crowley's Ridge. It's beenremoved by erosion between

(38:19):
Crowley's Ridge and Memphis, butit exists today underneath
westernmost Kentucky, Tennessee,and down into Mississippi and
southern Illinois, as I said,and is the principal aggregate
source for gravel in particular.
This was a very broadfloodplain. We estimate that it

(38:40):
was probably in the order ofover 100 miles wide. Now I'm not
saying the river was 100 mileswide by any means. The river
migrates back and forth, leavingbehind the sand and gravel as it
shifts, but it was a very bigriver, and our estimates are
that it was maybe as much as sixto eight times bigger than the

(39:04):
Mississippi in terms of volumeof water flow, and we base that
on what we have found in thesand and gravel deposits, what
look like ancient meander bends.
Meander bends, these are the bigcurves in the Mississippi River,
or any other river, for thatmatter. One of the bigger bends
today is the one up near, well,up in southernmost southeastern

(39:30):
Missouri, the New Madrid Bend.
That's what I'm trying toremember. There's very large
meander bend up there, but wehave found evidence in these
ancient deposits, these 3.6million year old sand and gravel
ancestral Mississippi stuff,that these meander bends were

(39:50):
substantially bigger than that,and for those meander bends
scaled to today would indicate asix to eight times greater
discharge of the 3.6 millionyear old river.
Now there's still lots ofcontention about the age of
these sands and gravels that I'mtalking about. We have some very

(40:12):
good dates from a quarry northof Memphis, and the people that
did the work were at Purdue andat a California school, it may
have been Berkeley, I shouldremember that, but any event,
they came to the conclusionthat, based on the samples that
we collected here in Memphisfrom a quarry, that these set

(40:37):
set-ups were deposited 3.6million years ago, so that's
where I keep throwing thatnumber around. It could have a
wide range of ages. It could bea very old river that extended
over millions of years, it'spossible.
But there's another PhDdissertation that's sitting out
there, sort of a plum hangingfrom a tree. Let's go to all

(40:57):
these different quarries, getsamples, determine the age of
that unit and nail it down.
When, when was that ancientMississippi River flowing? Our
best estimate right now is inthe order of 3.6 million years
ago, but it's hanging on athread. We've only got one
well-defined series of dates.

Dean Klinkenberg (41:21):
So, what would the conditions have been like at
that point in time, say 3.6million years ago, that might
have fed that much water intothe Mississippi?

Dr. Roy Van Arsdale (41:32):
Excellent question. Well, you, you could
have had 3.6 million years agomuch higher rainfall, but
there's no indication of thatfrom paleoclimate studies.
Nobody has ever proposed thatthis was an Amazon environment
3.6 million years ago. So wewere forced to consider the

(41:56):
possibility that the drainagebasin was substantially bigger
than what it is today, as youknow, the Mississippi River, the
eastern edge of the drainagebasin is the Appalachians, the
western is the Rockies, and thenorthern border is pretty much
the Canadian American border,and that that is the footprint
of Mississippi River. Well, youcan't really extend the drainage

(42:18):
basin further to the east,you've got a mountain range, you
can't extend it to the west,you've got a mountain range, but
there's no such mountain rangeto the north.
So we looked at the possibilitythat the Mississippi River
drainage actually started wellup into Canada. Not at the
Canadian American border, butwell up into Canada, so that we

(42:42):
can enlarge the drainage basinby including southern Canada,
southern central Canada as beingpart of that 3.6 million year
old drainage basin. Well, as weare doing this and formulating
these ideas and coming up with anumber of lines of evidence, we
came across a paper by someCanadian earth scientists, where

(43:03):
they had mapped river systems insouth and central Canada that
flowed across southern Canada tothe Red River area. Now, the Red
River, I'm talking about theNorthern Red River, the one that
flows today from thenorthernmost part of South

(43:26):
Dakota, let's just say fromNorth Dakota north to ultimately
Hudson Bay. Well, these guyswere saying that no, it looks
like the drainage was to theeast, and what if you projected
it would have gone into theMississippi River and, and
south, or at least weinterpreted, we interpreted as a

(43:49):
southern flow that would havecontributed the water that we
were looking for. So these guysprovided us with one of the
strongest lines of evidence at3.6 million years ago, southern
Canada was actually draining tothe Mississippi River and
ultimately to the Gulf ofMexico. We had other rungs of

(44:13):
evidence, but that was that'sthe best

Dean Klinkenberg (44:17):
Yeah, so just a much larger drainage basin.

Dr. Roy Van Arsdale (44:24):
50% bigger, thereabouts.

Dean Klinkenberg (44:25):
Yeah, so then I'm going to go out on a limb,
and I'm going to guess theglaciers changed all that.

Dr. Roy Van Arsdale (44:32):
Oh yeah, it just did a number on everything.
As you know, the ice accumulatedinitially in Canada, in this
part of the world, and as theice piles up, it spreads kind of
like pouring honey onto a table,you pour it at a point, but it

(44:52):
spreads all over the table, andso that's what was happening
during what we call thePleistocene, so you have a big
ice sheet advancing from Canada,from the Hudson Bay area, so
that any kind of drainage wouldhave been, would have been
destroyed, and that is to say,the original south flowing

(45:19):
drainage would have beendestroyed, because the area
would have been covered by ice.
The Canadian part of the storywas totally changed and covered
by ice. The advance of theglaciers had another profound
effect. It lowered sea level,that's where all the water came

(45:41):
from, that made the ice, and soas sea level went down, the
major rivers of the worlddraining into the oceans would
incise, and the MississippiValley, being made up of
relatively soft rocks, wouldhave been been like cutting hot
knife through butter, and so theMississippi Valley underwent
dramatic erosion when sea levelwas as much as 400 feet lower

(46:05):
than it is today. And so in sodoing, a lot of sediment of the
Mississippi River Valley wasremoved, and that ancient river
deposit of 3.6 million yearsago, most of it, or yeah, most
of it was eroded away, and wehave the carving of what is now

(46:29):
the Eastern Lowlands and theWestern Lowlands on either side
of Crowley's Ridge, which islocated in Eastern Arkansas.
So the modern landscape is aconsequence, in large part of
incision during sea leveldecline and erosion, and and

(46:52):
then superimposed upon that, asthe ice sheets melted all the
sediment that was trapped in theice, a large part of it would
have entered the river systemand was deposited in the
Mississippi River Valley, so wehave a lot of ice age sediments
in the Mississippi River, andthis, when I say, when the ice

(47:13):
melted, there were actually asperhaps as many as 18 glacial
advances and melt backs, sowe're talking about over two and
a half million years, dramaticchanges in sea level and ice,
the freezing and thawing, andfreezing and thawing, and with
each cycle you get erosion anddeposition, and it makes for a

(47:34):
very complicated picture.

Dean Klinkenberg (47:36):
Right, Right.
And then all of that sedimentbeing incised out of the valley
gets carried down to the Gulf ofMexico, right? And

Dr. Roy Van Arsdale (47:45):
Correct.

Dean Klinkenberg (47:45):
And it kind of, that must have helped build
that continental shelf that wesee today.

Dr. Roy Van Arsdale (47:51):
That's right. It certainly deposited
the large part of the sedimentpile that the oil companies are
exploiting for oil and gas. Andthe delta that we see today,
which is most people think of,at least geographically, the
delta being Louisiana, you know,that was, that was, that's all

(48:13):
very young sentiment within thelast 20,000 years, most that
deposited that, so there's beenthis seaward growth of North
America as sediments beingstripped off of the continent
and comes down the Mississippi.
So in this process, though the,where was I going with this? We

(48:44):
think that this southern flowagain had to be reversed, had to
be reversed, and so why is itthat the northern part of the
United States, in particular RedRiver, now, which apparently
used to flow south prior to theice ages, why is it flowing

(49:10):
north? Well, the ice sheet notonly expands and contracts by
growing and shrinking, I sayshrinking by melting. It also
has the effect of making thecrust of the earth sink. It's
kind of like stepping on on atrampoline, and the trampoline

(49:32):
surface drops because of theweight of you standing on it.
Well, the same thing happenswith this giant ice sheet on
Canada. It made the crust sink.
Well the melt, the ice meltsback faster than the rebound
occurs. The analogy, thetrampoline goes out the window

(49:53):
now, because the minute you getoff the trampoline, it jumps
back. But in this case, now withthe very slow, the encroachment
of the ice and the build up andthe thickening, it makes the
more liquid deep part of theearth, meaning the mantle flow
out from underneath that icecap. Okay, so the crust flexes

(50:17):
and bends down and pushes themore liquidy stuff out of the
way. Now, when the ice melts,that liquid stuff flows back in
to where it was, but it comes inat a much slower rate, much
slower rate than what the iceretreats incredibly quickly when
they, when you go out of a outof a glacial event, it takes

(50:43):
about 90,000 years for the iceto go to full maximum and reach
southern Illinois. It only takesabout 10,000 years for the whole
thing to melt away. So you knowit took 90,000 years to depress
the crust, but it only took10,000 years to take the weight
off, and so the crust is stilldepressed, which means that the

(51:05):
landscape slopes towards thenorth, towards Hudson Bay, and
that's why the Red River isflowing towards Hudson Bay
today, and why the drainage ofsouthern Alaska goes up to
Hudson Bay. That area was thedeep part when the ice first
melted. Alright, now you stillwith me on that?

Dean Klinkenberg (51:25):
Oh yeah, I'm following.

Dr. Roy Van Arsdale (51:26):
Okay, well, we know that the water flows
from North Carolina, NorthCarolina, North Dakota up the
Red River, as do the otherrivers of southern Canada, and
they flow ultimately up intoHudson Bay, but we also know
that Hudson Bay is coming up, asis all of southern Canada. It's

(51:50):
still rebounding from thatmassive ice sheet. We know this
from a number of reasons. Firstof all, it can be measured. It
has been measured. Hudson Bay iscoming up at 10 millimeters a
year, which doesn't sound likeabout a lot, but when you start
dealing with geologic time,that's an incredibly fast rate,
and in so doing it is tiltingthe landscape back to the

(52:17):
condition it was prior to theice ages. Okay. So if you're
doing that, the north flowingRed River is starting to tilt
back, and so that it's no longersloping to the north.
Eventually, it's going to slopeto the south. The Red River is
notorious for its floodingevents. All right, there's been

(52:42):
tremendous floods up along theRed River and up into Canada.

Dean Klinkenberg (52:46):
Just ask anyone in Fargo.

Dr. Roy Van Arsdale (52:48):
Yes, yes, there's some spectacular
photography of these towns upthere that are barricaded by
sandbags with water all aroundthem. Well, that there's a
number of reasons for that. One,of course, is that with Red
River flowing north to theNelson River into Hudson Bay,
those areas up north stay frozenlonger, and so the water gets

(53:12):
blocked by the ice to the north.
It can't flow to the northreadily because of the ice, but
the contributing factor is thatthe slope is shifting and
reversing such that weanticipate not that I'm going to
be around to see this but within10,000 years, assuming no
glaciers come back, we're goingto have southern Canada draining

(53:34):
back into the Mississippi Riverwhen that full isostatic rebound
of Hudson Bay takes hold, thewhole landscape is going to
return to what it was prior tothe ice ages, which is a
southern slope.
Now, there's another element tothis that we didn't really focus
on very much, we just mentionedit. This rebound, which most

(53:58):
people are modeling, is due tothe ice melting, right, very
clear. If you take a mile iceoff of off of a landscape, it's
going to come back up. Okay,it's going to come back up.
Well, what's not often, if it isat all taken into account, is
that there was a tremendousamount of erosion that took
place by these glaciers, so theyare removing rock as they are

(54:22):
moving south, they are braidingoff rock, which ultimately
enters the rivers and flows tothe Gulf. Well, if you remove a
couple 100 feet of rock, that isgoing to the response by the
crust is going to be reboundfrom that removal as well, so

(54:44):
not only do you, this iscompounded, it's not just ice
removal by melting, you also,the glaciers have removed
surface rock, which is going topromote rebound and make it even
perhaps greater than what it wasin terms of its original slope
to the south.
That was a mouthful, and Itotally overwhelmed your

(55:07):
audience.

Dean Klinkenberg (55:09):
No, it's really that is really intriguing
to think about. I don't know howmany people have had a chance to
do this, but I've been to thatarea around the Minnesota, South
Dakota, South Dakota, NorthDakota border area, where about
20 or so miles apart, Brown'sGap, I forget exactly what the
name of the spot is. On one sideyou have the Red River, the

(55:30):
beginning of the Red River, thenorth flowing north. On the
other side of that, you have thebeginning of the Minnesota River
heading south. So it's veryeasy, having been there, to
imagine at some future state,you know that the flow changes
just enough that that unitesagain. It's like a single river,
and all that water from what'snow the Red River, the North,
would then just be captured andgo down the Minnesota River

(55:51):
Valley.

Dr. Roy Van Arsdale (55:54):
Well, there's another potential. I'm
really going out on a limb here,but I hope your audience will
forgive me, but if this goes toas we think it will, you see the
Red River flows north to a biglake, north halfway up to the

(56:14):
Hudson Bay area, and then thatlake drains into the Nelson
River, into Hudson Bay. Okay,and the drainage is all to the
north, and I'm saying that nope,that's going to reverse. What we
don't know, we think we knowthat the actual point of
reversal is going to be in theNelson River area. So we have a

(56:38):
pretty good idea where theoriginal drainage divide was
where the northern limit of theMississippi River was, and where
it will be in the future.

Dean Klinkenberg (56:47):
None of this is going to happen while we're
alive. At what point in humanhistory should we be making
preparations for an increasedmuch larger Mississippi? Do you
think, few 1000 years?

Dr. Roy Van Arsdale (57:04):
We're talking thousands of years. Yes,
yes, I'm not going to be, I'mnot going to be a witness to
this, nor will you, even thoughyou're a younger man, you will
not be a witness to this either.

Dean Klinkenberg (57:15):
Yeah, not gonna be around for that.

Dr. Roy Van Arsdale (57:17):
Well, and we're also presuming there will
be no more ice ages, because ifthe ice comes back, the whole
cycle starts over again.

Dean Klinkenberg (57:25):
Right. Yep, you know, one of the things that
I really like about, about yourwork, and talking about this is,
I just, again, how it, itreminds us how much the planet
is continually changing, likethe geographic features of the
planet are not static. Youknow, we see a rock, you know,

(57:45):
and it seems so, you know,eternal in a sense, but none of
this is. All of these things arecontinually changing and be
affected by a variety of forces.
Even the Mississippi River,relatively speaking, is pretty
young when you think about theage of the planet.

Dr. Roy Van Arsdale (58:01):
Absolutely.

Dean Klinkenberg (58:02):
And and even during that time period, it's
been through some verysignificant changes, and I was
just thinking again about Ithink you did some work where
you were estimating differenttime periods for when the Ohio
and Mississippi River confluencechanged, or different periods of
time where those two rivers met.

Dr. Roy Van Arsdale (58:23):
Yes.

Dean Klinkenberg (58:23):
So can you just kind of summarize that for
us fairly quickly too?

Dr. Roy Van Arsdale (58:28):
Well, okay.
We today, of course, theMississippi River in Ohio joined
at Thebes Gap area in Cairo,Illinois. Okay, but if we go
back several 1000s of years ago,the point of junction, and this
isn't my work, this was done by,by, by someone else, the

(58:52):
confluence was actually south ofHelena, Arkansas, south of
Crowley's Ridge, and then itjumped up about midway, little
bit more than midway onCrawley's Ridge, and then it
jumped again a little bitfurther north, and then finally
moved up to its presentposition, and so the Ohio River
has pretty much captured thepresent Mississippi River at

(59:25):
Cairo, where they joined today.
In fact, I was having a similarconversation with some people
from from Ohio some years agoand pointed out that most of the
landscape of the MississippiValley is actually ancestral
Ohio River, and that theMississippi River used to flow

(59:49):
down the west side of Crowley'sRidge through what's called
today the Western Lowlands, andthe Ohio River flows down
through the Eastern Lowlands,which is what is today the
modern Mississippi. MississippiRiver, and that the Ohio has
sequentially captured theMississippi River in steps
further and further to the northto where it is today, and the

(01:00:10):
person's response was, well,then it shouldn't be called the
Mississippi River Valley, itshould be the Ohio River Valley,
and I had to say, "Yes, you'reright."

Dean Klinkenberg (01:00:19):
Yeah, well, we won't even get into the debate
about the Missouri versus theMississippi name, because in my

Dr. Roy Van Arsdale (01:00:21):
I'm sure there are.

Dean Klinkenberg (01:00:22):
So we've hit it at this a little bit, but I'm
part of the woods up here, mypart of the river, there's a lot
going to, what are some of thebigger questions in your mind
of fun, fun arguments over happyhours, where we don't have that
discussion. Soyet about that we don't know

(01:00:45):
about the geologic history ofthe Mississippi?

Dr. Roy Van Arsdale (01:00:51):
In my mind, see, my principal focus of
getting really diving into thehistory of the Mississippi was
to try to better understand theearthquake threat. That's where
most of my funding has come.
That's where I've done most ofmy publishing is the New Madrid
Seismic Zone. And it's stillquite the enigma as to why we

(01:01:13):
have big earthquakes in thecentral United States, and I
think it's related to theerosional history of the
Mississippi and Ohio rivers. AsI mentioned before, there has
been dramatic erosion eventsthat have occurred in the valley
during the ice ages. Now, if youhave an area that's under

(01:01:36):
compression, which North Americais, because it's drifting
westerly, it's being, if youwill, pushed by the Mid-Atlantic
Ridge, and it's driftingwesterly. The every all the area
east of the Rocky Mountains isunder horizontal compression,
right? It's just a fact. And itappears to be related to
continental drift in this, thisdrifting of North America,

(01:01:58):
pushing from the Mid-AtlanticRidge.
If you have a fault systemthat's being squeezed, and you
remove the cap off the top, ifyou remove sediment, hundreds of
feet of sediment off the top, itseems to me that that is a way

(01:02:18):
that you could activate theseancient faults, so I'm thinking
that the erosional history isvery important to better
understanding the seismichazards and the cause of
earthquakes, and what causesearthquakes, of course, is
fault, right, bedrock movement.
And if you can come up with amechanism to make the earth

(01:02:42):
move, then you have made anearthquake. And one of the ways
to do that is by removing a lotof sediment off the top of these
faults and releasing thevertical pressure on them, I
mean, we see similar thingsgoing on related to reservoirs,
they fill up a reservoir withwater and they start

(01:03:07):
earthquakes, they've changed thelocal pressure. Or that
earthquakes occur in parts ofScandinavia and Canada where the
ice has recently melted. Theyremove the weight of the ice,
and that ambient compression isbeing now released. So it seems
to me that looking at thegeomorphology and the geomorphic

(01:03:32):
history, specifically theerosional depositional history,
the valley. There may be a linkto why these faults have become
reactivated. You see, these areancient faults that have turned
on and turned off through deeptime, but they apparently have

(01:03:53):
turned on quite recently. Allright, within the last 5,000
years, something like that.
Well, that sits right in theframework of these big erosional
events that have have occurred.
So that's what I've beenthinking about and proposing.

Dean Klinkenberg (01:04:16):
So yeah, basically, if I'm following you
right on this one, then the meltwater is coming down from the
glaciers, and that range of5,000 plus years ago probably
removed an awful lot of sedimentas those major flows, those
massive flows of water camedown. Is that kind of what

(01:04:39):
you're thinking?

Dr. Roy Van Arsdale (01:04:41):
That is certainly part of it. Yes, you
see another aspect of theMississippi River. If you look
at the map of the MississippiRiver, it pretty much sits
against the bluffs. Okay, youhave a, you have a 50 mile or
more wide eastern lowlands, butthe river is over on the eastern

(01:05:02):
side of the valley, except atNew Madrid, where it takes this
big loop. Right, you may befamiliar with that big loop. The
reason it has a big, big loop isit goes around an uplift area.
That area is literally comingup. That's the focus of a large
part of the New Madrid seismiczone under that loop.

(01:05:22):
But if you look at the riverfurther south, it lays up
against the bluffs all the wayto south of Memphis, and then it
heads off to the west. I think,and I've argued that the
Mississippi River over the last20,000 years has shifted from
its position just east ofCrowley's Ridge, and migrated in

(01:05:44):
an easterly direction, erodingthe bluff line to its current
Memphis position. So that if wego back 20,000 years ago,
Memphis would have been 50 milesfrom the river. All right, so
this stripping of about 70meters of sediment, because
that's the height of the bluffs,about 70 meters, something like

(01:06:07):
that, I may be overstating that,but about 70 meters, I believe.
You have essentially, if indeedthat eastern migration story is
correct, you have stripped 70meters of sediment off of the
eastern part of the easternlowlands. The significance of
that is that's where all the,not all, where most of the young

(01:06:30):
faults lie, and where theseismicity occurs.
So, I think that this mostrecent stripping event, it may
be that which is responsible forthe onset of seismicity in the
Mississippi River Valleyrelatively recently, within
1000s of years ago, let's say10,000 years ago to present.

(01:06:50):
It's related to this eastwardmigration. Now you didn't ask
this question, but you'reprobably going to ask, "Why is
the Mississippi Rivermigrating?" Well, I think it's
related to the original erosionof the valley, and that it is

(01:07:10):
coming up all right. It iscoming up. The center of the
valley is Crowley's Ridge. Thehighest part of the valley is
actually in the center of thevalley, Crowley's Ridge, and
there's evidence that Crowley'sRidge has and continues to come
up, and that the MississippiRiver has shifted eastward, and

(01:07:36):
that the rivers on the west sideof Crowley's Ridge have shifted
westward, indicating that thecenter of the uplift is
Crowley's Ridge, and I thinkthat that uplift of Crowley's
Ridge is still a manifestationof the severe erosion that took
place when sea level dropped 400feet. It just basically removed

(01:07:59):
so much sediment that the valleyis still responding to that, and
coming up.

Dean Klinkenberg (01:08:09):
That's really interesting. I hadn't, I didn't
know Crowley's Ridge of thatarea that we still have some
uplift going on.

Dr. Roy Van Arsdale (01:08:16):
Well, it's nothing obvious, that's for
sure. But there's a paper justrecently published about young
faults along the margins ofCrowley's Ridge, and there may
be more information coming outon that subject in the near
future. Some colleagues and Iare working on that right now.

Dean Klinkenberg (01:08:36):
Excellent.

Dr. Roy Van Arsdale (01:08:37):
We haven't got anything to report quite
yet.

Dean Klinkenberg (01:08:40):
So I don't know if there's a single good
resource for this, but if folksare interested in going a little
deeper into understanding thegeology and the geomorphology of
the Mississippi Valley, arethere one or two books or
articles that you wouldrecommend to do so?

Dr. Roy Van Arsdale (01:08:56):
Well, if you're interested in the history
early American history, Penick'sbook. He's a historian, and was
a historian at University ofMissouri. Now there are two
editions. The later edition isthe one you should read, and the

(01:09:17):
history part is good, thescience is not. But then again,
he's a historian, so, and at theend, when he wrote the book,
most of the things I'm talkingabout today were not published
when he wrote that book, soanyway, so that if people are
really interested in what peoplesaw or witnessed, experienced,
Penick's book on the on thehistory of the New Madrid

(01:09:40):
seismic zone and the earthquakesof 1811, 1812 is a great read.
I have written a book on thegeologic history of the
Mississippi Valley, and inconjunction with an
archeologist, and the book ishalf geology, half archeology,
that might interest people, butit is a written for general

(01:10:03):
audience. In any event, I'mcertainly available if people
want to send me an email andhave a request. I will respond
to their requests as best I can,and you can go from there.

Dean Klinkenberg (01:10:20):
Well, Roy, that was fantastic. Thank you
for having this conversationwith me today. I really
appreciate you sharing yourexpertise, and you did a great
job of explaining things in away that I can understand. So,
I'm sure that's good enough foryou. That'll work for all the
listeners to this podcast aswell. So, thanks so much for
your time.

Dr. Roy Van Arsdale (01:10:38):
You're welcome. Bye, bye.

Dean Klinkenberg (01:10:41):
Thanks for listening. If you enjoyed this
episode, subscribe to the serieson your favorite podcast app, so
you don't miss out on futureepisodes. I offer the podcast
for free, but when you supportthe show with a few bucks
through Patreon to help keep theprogram going, just go to
patreon.com/deanklinkenberg. Ifyou want to know more about the

(01:11:01):
Mississippi River, check out mybooks. I write the Mississippi
Valley Traveler guidebooks forpeople who want to get to know
the Mississippi better. I alsowrite the Frank Dodge mystery
series that's set in placesalong the river. Find them
wherever books are sold. TheMississippi Valley Traveler
podcast is written and producedby me, Dean Klinkenberg.
Original music by Noah Fence.
See you next time.