Earth’s History Book


What we want to do here is kind of, we want
to take a look at the big picture, not just the big picture of here. We’re going to start
here, but we want to do the big picture as it applies to the world, the world of the
Permian, the world of what it was like then. And I’m going to start with Jerry. Can you
tell us where we are and what we’re seeing? Well, we’re up one canyon in Prehistoric Trackways
National Monument. I think it’s one of the more beautiful canyons. And one of the largest
trackway sites is right behind us. I call it AF10. And you’ve got literally hundreds
of these layers, and they’re like pages of a book. If we were to look at this whole mountain,
the red bed layer down here would be one volume, let’s say its a hundred pages long. And we
can look at all these tracks and these hundred pages, but what’s so cool about this whole
mountain is you’ve got the encyclopedia. So, you’ve got this volume and then this volume
and then this volume and then this volume. So, the cool thing about it is the Earth keeps
books. It records the history of life on this planet. And this is an excellent example of
a place that had a lot of activity that really, scientifically, we know virtually nothing
about. We’re right on the cutting edge of really understanding this period of time so
long ago. One of the things I want to touch on then
is these red beds. Something else that’s inside these red beds are plants. Yes. And Bill, could you tell us a little bit about
the plants and what that tells us or can at least, hints at in terms of the climate of
the past? Well, the plant diversity here is low, for
one thing. It’s primarily conifers, modern relatives, most people will be familiar, they’re
not close relatives, but things that you use for your average Christmas tree. And these
beds are variably full of them. And not a whole lot of diversity. So, as we saw in marine
rocks at some other point where there were many species here, you have a relatively low
variability in the types of plants. We presume that there were forests of these somewhere
nearby. How nearby, we’re not exactly sure, because they’re mostly floated into the environments
where we find them. So, we’re probably looking at some stands of conifers. These kinds of plants, as far as we know,
from the kinds of rocks they’re in and what the rocks tell us about climate and so on,
is that they’re in seasonally dry environments. So, probably looking at a landscape that has
rainfall, certainly, in it, but the rainfall is probably seasonably distributed. Let me go from that and come over here to
Spencer. We’ve heard that this is probably a seasonal environment, we’ve talked about
these red beds, the things that are on them. What were these red beds, or that we see here?
These thinly bedded, or in some cases, thicker bedded rocks? Right. Well, we know at this time that there
were mountains to the north of us and to the northeast. These are what geologists call
the Ancestral Rocky Mountains. And they were really created by the collision of the continents
that occurred some million years before these rocks were formed, or at least, they began.
So, as the continents came together to make one supercontinent, the crumbling of the crust
created what we call the Ancestral Rocky Mountains in the western United States. And from these
Ancestral Rocky Mountains, rivers were flowing down into vast flood basins. And this was
the edge of one of those big flood basins as it came down to meet the shoreline.
The red rocks you see are layers of sand and silt that represent what a geologist would
call sheet flooding, just literally, sand and water just being flooded over vast, nearly
flat surfaces. And those sheet floods were probably at the extreme ends of big river
systems that were to the north of us. So, the big rivers would have flown down out of
the Ancestral Rockies, they would have hit the flood basin. And then the basin was so flat that all that
would happen is there would be these vast floods where the red sand and silt came out
with water. And then, finally, here at it met the shoreline. So, these sands and silts
were deposited right along the edge of the Let’s take the, when you said to the north,
I think it’s a great segue, because now we can talk about where were we at this time?
If I take my GPS out today, right now, actually, I can’t tell you what the latitude is, I need
to take it out to see. 32 degrees. 32, there we go. But where were we when these
were being deposited? As far as we can tell, we were almost dead
on the equator. We were within a few degrees of the equator. So, we were in the equatorial
zone, the tropical zone. And this area was on the western edge of the vast supercontinent
which we call Pangea. So, there were shallow seas embayments along that western shoreline.
And this, I would call the Hueco Seaway, after the rock formation, the Hueco formation or
Hueco group. This Hueco seaway was in here, coming in from a bigger ocean that was out
to the west of us. And here in this equatorial tropic. And for this particular site, we’re going
to come back to Jerry, now. Because now I think we can see what the big picture was
for our continent. We can see what the general climate, hopefully, we can see, or at least
have an idea of what the general climate was like. And now, we can come back to these trackways
that Jerry found along with the plant fossils that are here and hopefully see the big picture
to the small picture. Well, what’s fascinating to me and when I
went to school and you get these little fossil books that have descriptions of all these
marine fossils and bones or skulls or teeth, things that everybody’s got. No plants. No plants. Sorry. plants. There wasn’t anything that had footprints.
And for some bizarre reason, I never in my wildest imagination thought of fossil footprints.
So, when I first saw three little fossil footprints in a case, I mean, I was stunned and I was
hooked. And I think the main reason was, if you think about how hard it is to make a footprint
and keep it a footprint for 280 million years. I mean, that footprint is still there. It
is a representative sample of a living creature. Bones, that tells us about the animal. It
doesn’t even necessarily tell us where it died. And we can try to put it together, but
we don’t really have a lot of confidence as to what it looked like until we find how these
animals moved. And with the dinosaurs, we used to think of them as heavy and plodding
and now we’ve got these really efficient, cool looking trackways and all that.
But anyway, here, you’ve got these layers and layers and layers of big tracks of pelycosaurs,
tiny tracks of small amphibians. You’ve got insects, arthropods, all kinds of various
types of living animals, all preserved on these delicate pages. And it tells us a lot
about how these footprints are made. They have to be a real deformable surface, but
it has to be protected. If there was a lot of wave energy, they would be destroyed. So, to me, it’s just a remarkable record,
even more important, I think, than finding an isolated skeleton that just has paid. It’s
just the record, the encyclopedia of the Earth writing about this whole period of time. It’s a record that we can see here, that maybe,
perhaps, other people will be able to see as well, that informs us not only of what
was, things were like here, but of the larger picture of the world.

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