OK, let's get into this. When you think about
truly monumental American geology, your mind
usually goes to the big names, right? Absolutely.
Grand Canyon, the Rockies, you know, the big
explosive volcanoes of the Cascades. Sure, classics.
But there is this. This massive, almost hidden
giant sitting right there in the Pacific Northwest.
A geographic feature so vast that its creation
literally rewrote the map of three entire states.
And what's more, it holds the key to understanding
why one of our most famous national parks is,
well, so volatile today. That is the perfect
way to put it. It's a paradox. And that's what
we're diving in today, the Columbia Plateau.
Right. And our mission for you. listening, is
to get past just the surface geography, you know,
the wheat fields, the high desert, and really
understand that this whole region is, in essence,
one enormous solidified snapshot of deep earth
history. A snapshot. I like that. Yeah. And we're
going to trace its surprising and incredibly
violent creation. We'll get into the physics
of how 6 ,000 feet of solid rock piled up. And
then we'll reveal its direct, undeniable, and
frankly astonishing connection to the geysers
and bubbling springs of Yellowstone. And that
connection, that link between a flat, high desert
in Washington and the famous thermal features
of Yellowstone, that's the real aha moment. That's
the one. It ties everything together. But before
we get there, we really have to establish the
sheer scale of this thing. I mean, it's almost
impossible to comprehend. This isn't just a patch
of high ground. No, not at all. It's an immense
geologic and geographic region. It spans huge
portions of Washington, Oregon, and Idaho. And
its location is key. Right. It sits right in
the middle, sandwiched between the Cascade Range
to the west, which is a classic volcanic arc
on a plate boundary, and then the Rocky Mountains
to the east. So it's inland, way inland. Exactly.
And that central inland location is what makes
its very existence such a profound geological
puzzle to begin with. And its fundamental identity,
we have to define this. It's a wide flood basalt
plateau. Right. Cut through by the Columbia River.
And we should probably sit with that term flood
basalt for a second because it tells you exactly
what this region is not. Yes. It is the absolute
antithesis of the classic volcano image. You
know, you picture Mount Rainier. Mount Hood.
You see a central vent, a peak, that classic
cone shape. A mountain. A mountain, exactly.
Flood basalts are totally different. This means
the entire region wasn't formed by slow, gentle
plate movement or even a singular explosive eruption.
It was formed by fissures. Fissures, so just
cracks in the ground. Long, massive cracks in
the Earth's crust that just opened up and unleashed
this overwhelming, sustained outpouring of superheated
liquid rock that literally... float across the
landscape like water. And outpouring is the right
word. And when we talk about the size of the
area that's affected, it really redefines the
word massive. It does. The plateau covers the
geologic region we call the Columbia River Basalt
Group. And the scale of that. Well, this is the
initial shock factor, always. The lava flows
literally engulfed about 63 ,000 square miles.
Wow. That's 160 ,000 square kilometers of the
Pacific Northwest. OK, put that in perspective
for me. 63 ,000 square miles is. It's roughly
the size of the entire state of Georgia or a
bit larger than England and Wales combined. And
the important thing, the so what here is that.
This land didn't rise up slowly like mountains
do. Not at all. It wasn't crustal deformation.
It was violently and geologically speaking very
quickly inundated by liquid rock. It's one of
the largest such events ever documented on the
planet. It's what we call a large igneous province.
L .I .P. L .I .P. Exactly. So we've got the enormous
scale of the where. Now let's dig into the when
and the how. This wasn't just a one and done
event, was it? Not even close. It was a process
that spanned deep, deep time. The time frame
puts us mostly in the late Miocene and early
Pliocene epochs. Now we're talking, what, around
17 to 6 million years ago? Roughly, yes. We're
looking at a continuous, relentless eruption
cycle that happened over a span of maybe 10 to
15 million years. That's, I mean, in human terms,
that's an eternity. But geologically? Geologically,
that is a remarkably short period for this much
material to be extruded. It really wasn't a slow
leak. It was a sustained gusher. 10 to 15 million
years of these huge fissure eruptions just flowing
over the landscape, one layer on top of the next.
It's just, it's hard to visualize that much sustained
activity. And remember, the lava wasn't coming
from a single point like a volcano. It was coming
from these immense... fissure systems. Imagine
cracks in the earth that are tens, maybe even
hundreds of miles long, just pouring out this
very low viscosity, incredibly liquid basalt
lava. Low viscosity, meaning it's really runny.
Super runny. It could travel massive distances
before it finally cooled and hardened so it didn't
pile up in a cone. Right. It spread out like
pancake batter on a giant griddle. That's a great
analogy. It spread out and covered pretty much
everything. And the cumulative effect of all
those flows is just staggering. If you were to
drill down today, The final thickness of all
that solidified lava reaches a maximum of more
than 6 ,000 feet. 6 ,000 feet. That's over a
mile deep. Over a mile of solid rock. And that's
1 .8 kilometers. In some of the deepest parts
of the basin, geologists think it could be closer
to 10 ,000 feet. 10 ,000 feet deep. OK, to give
you another analogy, if you took the Willis Tower
in Chicago, the Sears Tower, which is over 1
,400 feet tall. You'd have to stack four, maybe
five of them on top of each other just to reach
the depth of the rock foundation under parts
of Washington and Oregon. That really drives
it home, doesn't it? It's not a feature on the
landscape. It is the landscape. It's the foundation.
Exactly. And this is where it gets really interesting
because we move from just one simple massive
flow to a highly complex, readable geological
record. You mean it's not just one big block
of rock? Not at all. Because the eruptions happened
episodically over millions of years, it created
this meticulously structured record. It's made
up of seven major formations. So like layers
in a cake. And these formations, I assume they
tell a story. They're not just about different
ages, but maybe different chemistries, different
eruption styles. You've got it. The sequencing
gives us the precise history of how this... this
heat source behaved as the continent moved over
it. These are the layers geologists use to date
and correlate rock across the entire region.
Okay, so let's walk through them. What are these
seven layers? All right, so generally from the
oldest and deepest layer up to the youngest and
shallowest. Number one is the Steens Basalt.
Steens. This is often considered the initial,
the first big outpouring. These flows are critical
because they represent the very first moment
that plume of hot rock reached the base of the
lithosphere. And where do you find those? Mostly
in southern Oregon. Yeah. And their sheer volume
points to an immediate dramatic start to all
this activity. It's like the initial crack in
the continental crust. Okay, what's next? After
that, we have the Imnaha Basalt. It's named for
flows you can see near the Imnaha River. And
it represents a subsequent major pulse of volcanism.
You can tell it apart from the Steen's flows
by slightly different chemical signatures. So
geologists can fingerprint these different layers.
They can. And that brings us to number three,
which is really the main event, the Grande Ronde
Basalt. Grande Ronde. That one sounds important.
Oh, it is. The Grande Ronde Basalt is the single
largest volume of basalt in the entire group.
It accounts for an estimated 85 % of the total
rock volume. 85 % in one formation. 85%. This
formation alone is thought to have poured out
over just a few million years, which points to
a period of just unimaginable heat and productivity
from the mantle plume below. Wow. Okay, so that's
the big one. What follows that? Then you get
the picture of Gorch Basalt. You find this more
in central Oregon, and it shows that even while
the massive Grand Ronde flows were happening,
there were other localized, chemically distinct
eruptions going on. So multiple fissures were
active. Right. Then there's the Prineville Basalt,
another layer named for a location in Oregon.
Then number six is the Wannapum Basalt. These
flows are spread broadly across the plateau,
and they often have distinct physical features,
which give geologists really critical visual
markers when they're mapping. And the final one,
the top layer. And finally, number seven, the
Saddle Mountains Asphalt. These are generally
some of the younger flows. You find them at the
very top of the stack. And what's really cool
is they're sometimes interbedded with sediments.
Sediments like from rivers or lakes. Exactly.
And those sediments give us clues about what
the climate was like right before the volcanism
finally started to die down. Let's go back to
the Grand Ronde for a second. If that one formation
is 85 percent of the entire volume. What does
that tell you about the plume underneath? Was
it just like an initial super gush that then
tapered off? That's a great question. And yes,
that is absolutely the interpretation. The enormous
volume of the Grand Evrand suggests that when
the plume had, you can think of it as this vast
mushroom -shaped top of the mantle plume, when
it first slammed into the cold, rigid North American
plate. The melting was just instantaneous and
incredibly productive. It's like opening a massive
valve all at once. So that first deluge just
created the bulk of that 6 ,000 foot thick stack.
In a nutshell, yes. It quickly covered thousands
of square miles. The flows that came after it,
like the Wannapum and Saddle Mountains, were
still massive by any normal standard, but they
represented the activity. tapering off or maybe
the heat source shifting as the plate moved.
So it goes from being a geological catastrophe
to a complex layered history book. A very, very
thick history book. And remember, even these
seven major formations are broken down even further
by geologists into formal, informal members and
literally hundreds, if not thousands, of individual
flows. Every single flow representing its own
eruption event. Its own moment in time. It means
for about 10 million years, the Pacific Northwest
was just continually being repaved by molten
rock. Okay, so that structure is now clear. 6
,000 feet deep, 63 ,000 square miles, seven major
layers, all dominated by that incredible Grand
Ronde basalt. But now we have to talk about the...
The immediate mechanical consequence of all this.
You're pouring trillions of tons of new rock
onto the surface. How did the Earth's crust even
handle that? This is where we get into the mechanism
of subsidence. And it's a bit counterintuitive,
but it's a fascinating tradeoff driven by mass
displacement. A tradeoff. Think about it. As
that huge volume of molten rock, the magma, came
to the surface, it didn't just appear out of
nowhere. It came from the mantle below. Right.
It had to leave a space behind. It left a relative
void. This rapid evacuation of material from
beneath the lithosphere created a space. So instead
of the surface being pushed up, which is what
happens when mountains form. The opposite happened.
The opposite happened. The very movement of mass
from deep underground to the surface meant the
crust above had its foundational support literally
pulled out from under it. And at the same time,
you've got the incredible weight of the new basalt
flows pushing down. Precisely. That tremendous
load, combined with the evacuation of the material
underneath, caused the Earth's crust to gradually
sink into the space left by the rising lava.
So the plateau is actually a depression. It is.
It's a large, slightly depressed lava plateau.
It created this broad basin. The plateau is literally
a depression because of the sheer volume and
weight of its own creation. It's a wonderful
piece of geological irony. Which means the center
of the Columbia Plateau is actually a bit lower
in elevation than the mountain ranges around
it, even though it's covered by miles of rock.
That's exactly right. It defined the entire regional
topography. Now, this massive event didn't happen
in a vacuum. It was interacting, often violently,
with the geography that was already there. And
nothing would have been more affected than the
biggest feature of all the ancient Columbia River.
Absolutely. The river was directly confronted
by these northwesterly advancing lava flows.
Remember, this basalt was incredibly liquid.
It moved fast. So it didn't just go around the
river valley. It didn't care about the river
valley. The flow was so overwhelming it just
poured right into the existing stream valleys,
filling them up completely. This often forced
the river to just stop flowing for a while or
scramble to find entirely new channels. It's
the ultimate geological obstruction. Just imagine
a river valley. and then a mile -thick layer
of liquid rock pouring across it. You can imagine
the steam, the explosions, as the water flashed
to vapor. But that filling action wasn't just
destructive. It was also critically constructive.
How so? Well, when the lava finally hardened,
often creating those huge distinctive columnar
basalt patterns you can see today, it formed
natural dams. Oh, of course. Dams hundreds of
feet high. And these natural dams backed up the
water, causing these massive impoundments. They
created temporary but often really extensive
lakes all across the landscape. So the flow had
this incredible two -sided power. It didn't just
pave over old land, it forcibly rerouted one
of the continent's major water systems. And the
current course of the Columbia River, especially
where it cuts through the gorge, is largely a
result of the river being repeatedly blocked
and then forced into new, deeper channels by
the relentless movement of that lava. It had
to carve its way through some of the hardest
rock imaginable. And you mentioned those temporary
lakes. It's in those impoundment sites, right?
the ones created by the hardened basalt dams,
that we find something almost paradoxical. It
is. We find one of the most exciting parts of
the plateau's formation. The paleontological
fossil record. I just find this transition phenomenal.
You have this massive, destructive volcanic event
that, by complete chance, creates the perfect
conditions for preserving the tiny details of
the life it was displacing. It's all about the
conditions. When you have a calm, deep, still
body of water, like a lake, and you have fine,
sediment -like volcanic ash or silt building
up very quickly. You get a low -oxygen environment.
You get an anaerobic, low -energy environment.
It's a perfect laboratory for preservation. The
lake beds became these incredible time capsules
entombed between layers of hardened basalt. So
what are we actually finding in these Miocene
-era lake beds? The detail is just astonishing.
We find beautiful, incredibly detailed fossil
leaf impressions. From what kinds of trees? We're
talking about capturing the whole flora of the
Miocene. Sycamores, oaks. Other trees that tell
us the climate was much warmer and wetter than
the semi -arid plateau we know today. These leaves
would just settle to the bottom, get trapped
in fine silt, and then instantly get covered
by the next eruption's fine ash or the next flood's
sediment, perfectly preserved. So you can literally
reconstruct the ancient forests that were there
right before or even during the eruption cycles.
That's the goal. We also find vast quantities
of petrified wood, sometimes in logs. hundreds
of feet long, which speaks to just how extensive
these ancient forests were. And what about smaller
things? Critically, we find exquisitely preserved
fossil insects. They're tiny, but they are crucial
data points for understanding the precise temperature
and ecology of the Miocene era. Insects? Wow.
And larger life. Does any animals get preserved?
Yes. And this is perhaps the most compelling
part. The bones of vertebrate animals. Researchers
have uncovered remains of large mammals, including
ancient rhinos, horses, even early camels, which
were once abundant in North America. So the remains
got trapped in the lake mud. Trapped in the soft
mud, quickly buried, and then sealed off by the
surrounding basalt. It gives us this amazing
window into the fauna of the Northwest before
it became a 6 ,000 foot deep slab of rock. The
destruction literally created the preservation.
That is just remarkable, moving from the scale
of a planetary upheaval to the microscopic detail
of an ancient insect wing. But now we have to
get back to the central, most challenging puzzle
here. The big one. Everything we've talked about,
the volume, the scale, the 10 million year time
frame, it all points to a process that should
be happening at a... plate boundary, where the
crust is being stretched or subducted. But the
Columbia Plateau is far inland. Hundreds of miles
from the Pacific plate boundary. So how could
an area so far from a plate boundary experience
such an enormous outpouring of lava? That is
the core geological question. It challenged scientists
for decades. Tectonic theory, as it was first
understood, just didn't have a clean answer for
this kind of massive inland volcanism. It required
thinking outside the box. or rather outside the
movement of the plates themselves, the evidence
was clearly suggesting some kind of concentrated
non -traditional heat source was melting rock
right at the base of the lithosphere. It had
to be concentrated and it had to be persistent.
So the detective work began. What is feeding
this giant furnace and why is its influence visible
across such a vast linear distance? And to solve
this, scientists undertook this incredible feat
of geological detective work, right? Using radiometric
dating. Sophisticated radiometric dating techniques.
They established precise hardening dates for
thousands of individual lava flows. and volcanic
rocks across the entire Pacific Northwest. They
were just looking at the big picture anymore.
They were looking for a pattern, a trail of evidence.
And what they found was the ultimate clue. It
was a temporal -spatial correlation that links
this inland flow to the biggest thermal anomaly
in North America today. So walk us through that
key discovery. What was the pattern? The key
finding was just startlingly elegant. When they
mapped out all the ages of the rocks, the youngest
volcanic rocks, the most recently active ones,
they were all clustered right near the Yellowstone
Plateau in the east. Okay. Conversely, the farther
west they went, back into the massive flood basalts
of Washington and Oregon. The older the lavas
were. The older and older they got. This wasn't
a random scattering. It was a perfect linear
timeline, a continuous chronological track stretching
nearly 500 miles across the continent. The rocks
were essentially dating themselves, creating
a perfect geological breadcrumb trail. Exactly.
The entire Columbia Plateau was revealed to be
the older, solidified part of a continuous ongoing
event that is currently culminating in the intense
activity we see at Yellowstone today. And this
unmistakable pattern led directly to the dominant
theory. The most probable explanation, the deep
mantle plume, or hotspot theory. This theory
says that an extremely hot plume of deep metal
material is rising all the way to the surface
right beneath the Columbia Plateau province.
Now, we've heard this theory applied elsewhere.
Hawaii is the classic example. Hawaii, Iceland,
they're the prime examples. Massive volcanic
systems that are nowhere near a major plate boundary.
But let's talk about the physics here because
it's immense. Where is this heat coming from?
Right. What's the source? The source is at the
deepest layer of the Earth we can really access.
The concentrated heat originates from a temperature
instability that develops. Well, for reasons
we don't fully understand, but it's at the boundary
between the Earth's core and its mantle. The
core -mantle boundary. How deep is that? It's
roughly 2 ,900 kilometers or 1 ,800 miles beneath
our feet. This is the deepest, most sustained
furnace we can conceptualize. That is truly mind
-boggling depth. We are talking about a heat
source that originates almost halfway to the
center of the Earth. Precisely. And this tremendous
heat triggers a plume, a buoyant column of superheated
rock that could be hundreds of kilometers in
diameter. Because it's hotter, and less dense
than the rock around it, it just ascends directly
up through the mantle. All the way to the base
of our tectonic plate. All the way. And when
it hits the bottom of that cold, rigid continental
plate, it causes massive decompression melting,
which then erupts as the flood basalt we've been
talking about. And here it is, the core revolutionary
concept that connects the entire story. The mechanism
that allows this to happen in the middle of a
continent is that the hotspot itself, that deep
mantle plume, is stationary. It's anchored. Deep
below the crust, completely indifferent to what's
happening on the surface. Correct. So the elegance
of this theory is its simplicity. The North American
plate is moving over it. Yes. Think of the hotspot
as a stationary, high -intensity industrial torch
just anchored deep inside the Earth. In the North
American continent is this immense conveyor belt
just passing slowly over the flame. That's the
perfect analogy. The hotspot burns a long, sequential
track onto the bottom of the plate. So those
massive 6 ,000 -foot deep flows we talked about
in Washington and Oregon. They're just the old
scars. They are the ancient scarring left by
that initial powerful thermal event. They were
created when that part of the North American
plate was sitting directly over the most intense
part of the heat source 10 to 15 million years
ago. And as the plate continued its steady journey
to the northeast. It carried the solidified Columbia
basalts with it away from the heat source. And
today, millions of years later. The North American
plate is positioned so that the hot spot is now
sitting directly beneath the Yellowstone National
Park region. That's the whole story. The track
starts in the far west with the oldest flows,
the Steens and Grand Ronde forming the vast basalt
plateau, and it just sweeps up to the Yellowstone
Plateau, which is the current location of the
youngest, most powerful volcanic activity. So
the whole thing provides this superb record of
the rate and direction of plate motion. It's
a geological tape measure stamped right onto
the continent. It is the ultimate aha moment.
The Columbia Plateau isn't just a place, it's
a history. book recording our continent's physical
journey across the globe. But just to be thorough,
while this hotspot theory is widely accepted,
are there any credible counter -arguments? For
the listener who follows this stuff, it's important
to acknowledge where the scientific debate is.
That's a crucial point. While the deep plume
model is dominant because it just so elegantly
explains the linearity and the sheer scale of
it all, some geologists have proposed alternatives.
Okay, like what? Often involving shallower mantle
processes. For instance, some models suggest
that maybe the initial rifting and extension
caused by the Cascade's subduction zone far to
the west might have allowed a more passive upwelling
of the mantle. Which would mean you wouldn't
need a deep, core -anchored plume. The heat source
would be a result of the plate itself ripping
apart and letting the ambient heat escape. Exactly.
But the problem with that is the timing of the
eruptions, the incredible volume, and that clear
chronological track leading directly to Yellowstone.
At the end of the day, the evidence is just overwhelming
in favor of a fixed deep heat source. The deep
bloom theory is by far the strongest candidate.
And of course, the modern visible evidence of
this active process is just impossible to miss
if you go to Yellowstone. Oh, absolutely. Yellowstone
with its iconic geysers like Old Faithful, the
mud pots, the steaming fumaroles. It provides
all the visible evidence you could ever want
of the concentration of heat right beneath the
surface where that hotspot currently resides.
All that bubbling, all that heat. It's the current
manifestation of the exact same mantle plume
that caused the Grand Ronde basalts to erupt
millions of years ago. It's the current. active,
and highly visible end of that 63 ,000 square
mile trail of ancient lava. It really makes you
look at the entire topography of the Pacific
Northwest completely differently. You go from
seeing a flat, high desert region to recognizing
it as this giant solidified wound left by a planetary
heating element moving beneath the continent.
A wound is a good word for it. So let's move
from that deep time geology to the world we actually
live in. We need to ground this enormous geological...
formation in our modern reality. We need to connect
the 6 ,000 feet of basalt to the ecology, the
resources, and the human communities that live
on its surface today. Right. And that transition
is fascinating because the geology really does
dictate the biology. The plateau's surface terrain
is globally classified by ecologists as the Columbia
Plateau Eco -Region. And what category does that
fall into? It sits within a massive global category.
the near -arctic temperate and subtropical grasslands,
savannas, and shrublands ichor region. So even
though the foundation is volcanic rock, the environment
itself is defined by being dry, by aridity. Yes,
and that aridity is also a result of the geology,
isn't it? The sheer height of the Cascade Range
to the west creates a monumental rain shadow.
Oh, of course. The Cascades block all the moist
air coming off the Pacific. Exactly. And that
leaves the inland plateau dry and semi -arid.
But the basalt foundation defines more than just
the climate. It defines the soil. Right, because
the plateau is famous for its agriculture, but
you can't be planting wheat directly into 10
million year old basalt. You certainly cannot.
So how does that deep hard rock layer support
the famous agriculture of the region? The wheat
fields around Pullman, the potato fields in the
Tri -Cities. That must be what's on top of the
basalt. It is. The critical link is laga soil.
After the basalt's cooled and we're... covered
by ice age sediments, massive continental winds,
blue fine, glacial silt that's lawless from the
now dry lake beds and river floodplains. So windblown
soil. Exactly. This silt settled on top of the
basalt, often accumulating into these thick,
fertile, windblown drifts that are incredibly
rich in minerals and deep enough to sustain massive
crops. The basalt is just the solid waterproof
container for that rich soil. So the 6 ,000 feet
of basalt is the container in the base, and the
fertile top layer, the loess, is the result of
post -volcanic glacial processes, a two -stage
process. And that foundation dictates the soil,
the hydrology, and fundamentally how communities
developed. It's helpful for you listening to
realize that so many major population centers
of the inland Northwest are literally built right
on top of this dense feature, relying on its
characteristics for survival. Let's make this
tangible. Let's use that list of specific cities
we compiled. Looking at Washington, the cities
on the plateau really show the diversity of the
region, but they're all tied together by that
basalt foundation. Absolutely. In the eastern
half of the state, you have a major urban center
like Spokane, which sits on the northern fringe
where the basalt meets glacial deposits. You
got Yakima, known for its fruit and hops, which
relies on irrigation from the plateau's resources.
And then there are the Tri -Cities Pasco, Kennewick,
and Richland, a crucial point where the Snake
and Columbia Rivers meet, where the hydrology...
is entirely controlled by those deep basalt layers.
And don't forget the agricultural and university
towns. Moses Lake, Pullman, which is famous for
the Palouse Hills covered in that thick loess.
Walla Walla, a famous wine region whose soil
is heavily influenced by the basalt. Then Ellensburg.
Colfax, Goldendale, the list goes on. And if
we move south into Oregon. It's a direct extension
of that same basaltic landscape. You find Pendleton,
famous for its wheat, Hermiston, Hood River,
where the Columbia River Gorge cuts deep into
the basalt, the Dallas, Athena, and Milton Freewater.
And finally, extending into Idaho, the plateau's
influence is clear there too. It is. Coeur d
'Alene, though it's nestled near the Rockies,
it sits adjacent to the basalt flows. You have
Lewiston. which is situated in a deep, lava -carved
canyon at the confluence of the Snake and Clearwater
Rivers, and Moscow, home to the University of
Idaho, sitting on those same rich, palouse lower
soils as Pullman. The takeaway here is that when
you drive between any of these cities, you're
not just crossing flat land. You're driving over
an ancient, complex, 6 ,000 -foot -deep history
book. The land might look flat or gently rolling,
but that rolling topography is just the surface
of what is essentially an enormous solidified
oceanic style crust sitting hundreds of miles
inland. And the existence of this massive block
of hard rock has created several other related
regional features, especially how water has tried
to, well, destroy and then utilize the work of
the lava. Indeed. And the first related feature
is absolutely crucial. It's the antithesis of
the smooth lava flow. The channeled scablands.
Sablands. These are intricately carved, often
bare rock channels and deep gorges, right? Etched
into the basalt surface by catastrophic glacial
meltwater floods, specifically the Missoula floods.
So this must have been an incredible battle between
ice and fire, geologically speaking. The basalt
was the immovable object, and the Missoula floods
were the unstoppable force. That's a perfect
way to put it. And the floods happened long after
the basalt had cooled. The sheer hardness and
thickness of the basalt provided this formidable
canvas. So when the gigantic ice dams broke,
unleashing volumes of water equal to all the
world's current rivers combined, the water couldn't
easily penetrate the basalt. Instead, it just
stripped away the lowest soil on top and carved
those huge, stark, channelized landscapes right
into the solid rock below. The scablands exist
because the underlying rock was so unbelievably
hard. So the plateau provided the hard canvas
and the Ice Age floods were the geological chisel.
Exactly. And that leads directly to the Grand
Coulee, one of the most famous features of the
scablands. This is a massive ancient riverbed
carved deep into the basalt by those same floodwaters.
It's an enormous trench, hundreds of feet deep
and miles wide. Which now defines the irrigation
and water systems for the whole region, including
the Grand Coulee Dam. The very same. And finally.
Beneath all of this hard rock that resisted erosion,
we find the one resource that sustains all those
cities and farms, the Columbia Plateau aquifer
system. This connects perfectly back to the layering
you were talking about earlier. It does. Water
can't flow through solid rock. Yeah. But it can
flow through fractures, joints, and critically,
between the separate layers of those seven basalt
formations. The way the water interacts with
the cooling fractures in the sedimentary layers
within the basalt determines the availability
of groundwater for everyone. So the basalt is
both the container and the filter for the water.
Making it directly linked to modern human survival
and agriculture. So we have a region forged by
internal heat from the Earth's core, solidified
into a deep layered structure, then sculpted
by massive Ice Age floods, and now sustaining
civilization through the water trapped within
its own solidified layers. It's a geological
legacy that is complex far beyond what you just
see on the surface. Which brings us to our final
moment. We've covered the ground, literally and
figuratively. Let's do a quick deep dive summary.
Okay. We established the staggering scale. The
Columbia Plateau is a vast, large igneous province
covering 63 ,000 square miles. It's built from
multiple formations, like the dominant Grand
Rhone Basalt, reaching a depth of more than 6
,000 feet, all piled up over a rapid 10 to 15
million years. We detailed the mechanics, the
incredible weight of the lava. caused the crust
to subside, creating that depressed plateau.
And it simultaneously rerouted the mighty Columbia
River. And those resulting lava dams created
temporarily lakes that acted as perfect time
capsules, preserving invaluable fossil records.
And we reveal the scientific astonishment that
this massive volcanism happened far from a plate
boundary. Because the plateau is the historical
track left by the North American plate moving
over a stationary deep earth hotspot, which is
currently centered right beneath Yellowstone
National Park. The entire basalt field is astonishingly
a physical tape measure documenting the rate
and direction of continental drift. That's the
core of it. So we understand the past and we
understand the present activity in Yellowstone.
But what does this all mean for the future? We
always like to end with something to mull over,
a final provocative thought. Well. If we accept
the evidence that the mantle plume is stationary
anchored near the core mantle boundary and that
the North American plate is moving over it at
a measurable clip, then the concentration of
heat currently visible as the spectacular geysers
and fumaroles of Yellowstone National Park is
actively migrating away from its current location.
It's not a question of if the activity will cease
in the Yellowstone region, but when. Exactly.
The current dramatic thermal activity will eventually
wane and die out as the North American plate
slides off that stationary plume, just as the
land that is now the Columbia Plateau flowed
past it 10 million years ago. So the history
of the plateau isn't just a record of the past.
It's a clear prediction of the future. The hotspot
will inevitably begin to affect new regions farther
to the east or northeast. If this geological
process continues on its current trajectory,
the question isn't whether the geological record
will continue to be written, but what part of
the continent will be next to experience the
surface expression of that immense, unmoving
furnace thousands of miles below? Will we see
new flood basalts erupting in, say, Montana?
Or maybe even farther east millions of years
from now, starting the entire process all over
again? The legacy of heat continues to write
its story across the continent, reminding us
that no landscape, no matter how settled, is
truly fixed in time.