[ Birds chirping ]
[Katelyn Salem:] "If you don't know history, then you don't know anything.
You are a leaf that doesn't know it is part of a tree."
This quote is from one of the greatest philosophers of ancient history...Michael Crichton.
And I think it does a good job of explaining why
we're about to take the two most boring school subjects,
history and geology, and squish them together.
With that, let's start where every great story starts,
[ Angelic ahhs ] the Bible.
Actually, people were writing about geology
long before the Bible. [ Banjo music plays in the background ]
In the 4th century BCE, Aristotle hypothesized that the Earth changed very slowly.
Slowly enough that it couldn't be observed during a single lifetime.
Aristotle's successor, Theophrastus, later wrote a book
following Aristotle's theories called "On Stones,"
in which he described, among other things, [ Lighter sparks up ]
how various rocks and gems
[ Fire roars quietly ] reacted when heated up.
In the 1st century CE, Pliny The Elder wrote what might
be considered the first encyclopedia set, called "Natural History."
In books 36 and 37, he describes a number of minerals and gems,
and even details a hardness test for telling fake gems from real ones
depending on whether they can be scratched with a steel file or not.
People may have been studying rocks
for much of recorded history [ Angelic ahhs ]
but for the history of modern geology, we need to start with the Bible.
[ Waves crash ]
In the book of Genesis, the Bible describes a great flood,
which God uses to reset creation, ridding the world of evil men,
and allowing a select few moral and just humans to repopulate the Earth.
By the 1600s, the prevailing theory was that proof of
the great flood could be found in the Earth's strata.
Strata are the Earth's distinct layers of rock or soil.
Like, this one might be all granite, while this one might be sandstone.
But the Biblical story didn't fit with the theories of some.
In 1666, Danish anatomist Nicolas Steno was dissecting a shark.
He noticed that the shark's triangular teeth resembled things known as "tongue stones,"
which were sometimes found embedded in rocky formations.
[ Dragon roars ] People believed these stones
to be the petrified tongues of dragons or snakes.
And actually, our old friend, Pliny the Elder, 16 centuries earlier,
thought the stones fell from the sky during lunar eclipses.
[ Soft, echoey chanting ]
But Steno instead thought,
"If tongue stones look an awful lot like these shark teeth…
maybe they ARE shark teeth!"
He believed that maybe, over time, the actual structure
of the shark's teeth was replaced by minerals,
keeping the teeth in the original triangular shape.
But then, how were the teeth getting embedded into rocks?
[ Rocks clack against each other ]
Steno wondered if perhaps dirt and minerals in bodies of water
would settle to the bottom to form horizontal layers over time.
[ Squirtle squeaks ] New layers would form on top of old layers,
trapping whatever remained underneath.
To test his theory, he began studying cliffs in Italy,
which led him to formulate three basic principles which geologists still use today.
The first is The Principle of Superposition.
This explains that if a sequence of rock has been undisturbed,
the oldest layer will be on the bottom, and the youngest layer will be on top.
Easy peasy.
The second is The Principle of Original Horizontality.
This explains that all strata form horizontally.
It's worth noting that we've since discovered minor exceptions,
such as the way sand accumulates on sand dunes.
Thanks to gravity, deposits generally don't
[ Blow dryer turns on ] form slopes greater than 45 degrees.
We can use this principle to conclude that these layers,
of Bow Fiddle Rock in Scotland,
were probably tilted by an earthquake or uplift or...some other force.
The third principle is The Principle of Original Lateral Continuity,
or TPOOLC, for short.
[Dwayne:] Ahem.
[Katelyn:] (Dejectedly) Yeah, you're right.
No one calls it that.
Anyway...
The Principle of Original Lateral Continuity explains that strata form
as unbroken, continuous layers of rock that will eventually thin out to nothing,
or end at the edges of a basin if they happen to be filling one.
Strata that are no longer connected must have been fractured by a force,
or separated by erosion,
like you can clearly see at the Grand Canyon in Arizona.
Using these three principles, we can understand the relationships
between a rock layer's age and its position in the rock record.
The study of that relationship is known as stratigraphy.
Now, with Steno's contributions to our understanding of stratigraphy,
he's sometimes thought of as "The Father of Geology,"
or sometimes "The Father of Paleontology," for his revelations about fossils.
However, most people consider the "The Father of Geology"
to be a Scottish farmer of the 18th century by the name of James Hutton.
In 1788, Hutton visited Siccar Point, where he found nearly vertical layers of greywacke,
covered with horizontal layers of red sandstone.
He reasoned that the only way something like this could have happened
was over a huge length of time, [ Rock scrapes ]
allowing the grey rock to be tilted or eroded [ Sand clatters ]
before the red rock settled on top.
Hutton thought these layers in the ground came from
"materials furnished from the ruins of former continents"
and that, every day, the same processes that are eroding
away large bodies of rock are also building up mountains.
He called this process
The Great Geological Cycle, [ Angelic ahhs ]
and hypothesized that it had been happening endlessly, forever.
Unfortunately Hutton's theory wasn't made popular
until after his death,
when Charles Lyell published the book "Principles of Geology."
His theory originally became known as uniformitarianism,
an alternative to the Bible's theory of catastrophism,
where the Earth was formed by catastrophes like the flood.
It followed the notion that the same geological processes that are happening now
probably happened the same way in the past.
Thus, we can figure out what happened then by looking at things now.
The name uniformitarianism eventually fell out of favor,
since, you know, almost nothing about the Earth is uniform.
The term actualism was taken up instead, [ A harp is strummed ]
since geologic time can be explained through actual processes that actually happen.
Actualism has had a huge impact on science,
extending even beyond the reaches of geology.
[ Low, slow motion impact ]
Charles Darwin himself used the concept of actualism
to understand that, much like the Earth,
life itself was also changing slowly over time.
[ Tribal music swells ]
Without a developed understanding of geology, Darwin could not have written
"On The Origin of Species."
Speaking of "origins," I hope you'll join us next time,
as we explore the origin of... well…
everything!
[ Fiddle music ]
[ Birds chirping ]
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