Untold Earth

Petrified Forest National Park preserves an important period in time.

About 220 million years ago, an interesting time period because it's actually bracketed by two mass extinctions.

Petrified Forest National Park is probably one of the most underappreciated national parks in this part of the United States.

We really do have one of the largest concentrations of petrified wood here at the park, where you can really study how animals and plants change over time.

In places like Petrified Forest, where climate change is preserved as a record in the rock, we have a standard that we can use to compare against changes that we're actually observing around us today.

Petrified Forest National Park is a time capsule filled with ancient trees that have crystallized over millions of years, essentially turning to stone.

What secrets do these fossilized ecosystems reveal about the prehistoric past, and how can they help predict the future of life on Earth?

Petrified Forest National Park is one of the most complete records of the end Triassic in the world.

It is a really interesting area to study how species were recovering from a mass extinction, and diversifying, and then dealing with challenges in the future.

There's no better place to see Late Triassic rocks exposed in such completeness and in such such glory.

At the start of the Triassic period, the area that we now call Arizona was, on the leading edge of a supercontinent that we call Pangaea.

This diagram here is what geologists call a stratigraphic column, and it is a graphic representation of the sequence of rocks that's exposed here at Petrified Forest National Park.

Most of this is the Chinle formation, which is the Upper Triassic, and all of the fossils that are associated with it, the magnificent badlands topography that you get where these rocks are exposed at the surface.

Over 200 million years ago, this was a lush tropical floodplain where massive trees thrived along rivers.

When those trees fell and were buried under layers of sediment, groundwater rich in silica from volcanic ash seeped in, gradually replacing the wood with crystals of quartz, preserving the stunning logs we see today.

There's a similar process, for how the wood is petrified to how the fossils are fossilized as well.

So this is a trail that kind of winds through a bunch of these huge petrified logs that we have here.

Part of the permineralization process is certainly helped by abundant silica.

And the volcanic ash is full of silica.

We see a lot of evidence of volcanism in volcanic ashes in some of the rocks, and we see pebbles and cobbles, just little round pieces of rock that eroded out of those volcanoes.

And we can see those here.

These plants and animals would die, become buried in water and sediment and fossilized.

They'd all be preserved together, kind of giving us a picture of the entire ecosystem.

In order to find fossils, you need a certain set of conditions.

So you need rocks of the right age.

And you also need them to be exposed at the surface.

Areas like Petrified Forest really are ideal to look for fossils.

Being in this desert landscape with, badlands and monsoon rains and cycles that really bring in a lot of erosion.

They're constantly exposing new fossils, constantly exposing new things that we can find.

The Triassic period ends where it does is because that is a time that's marked by a major mass extinction event.

And the proximate cause of that mass extinction is said to be climate change.

The climate change was probably triggered by atmospheric changes, carbon dioxide pulses, that were brought about by the breakup of supercontinent Pangea and the eruption of unusually large volumes of magma as lava at the surface, bringing with it these gases.

Various lines of evidence, including isotopes, tell us that conditions were getting warmer and drier over the course of the Triassic.

And so it is, good area to kind of study how animals are responding to these climate events.

We do see an extinction event at the end where only certain animals make it through.

Species that are more specialized typically have a harder time during extinction events if they have, really specific environment that they live in or a specific food source.

What we're seeing today is much faster, much different from what nature has done.

And we really can only attribute it to the activity of human beings through burning of fossil fuels, manufacture of cement, deforestation, and so on.

What we find is that what's going on now is happening at a markedly greater rate than anything that we can discern in the geologic record, except for the very brief catastrophic events that have happened, like meteorite impacts, for example.

Animals that are tied to specific environments might have a harder time, like animals that are semi-aquatic and need both land and water.

The oceans can also struggle through climate events, through ocean acidification, really kind of just the species that are more generalized will likely be able to adapt more and we'll start seeing specialists disappearing first.

If climate change that we see now is a purely natural event, it will be millions and millions of years long past any of our lifetimes.

But we're seeing things in our lifetimes.

So we have to use the outdoors, the rocks that we see, the national parks, the everywhere that we can go and study rocks and deposits.

We can learn from them about what is going on on the planet today and what we can think might happen in the future.

There's a lot that we can learn from Earth's history.

There's 4.6 billion years of Earth's history.

There's so many past time periods, past extinction events, that we can look back on and see how these animals did through different types of events and see how life recovered after.

And really just is the best tool that we have to kind of make predictions moving forward.