Hi. It's Paul Andersen and this disciplinary core idea ESS2B. It's on plate
tectonics and large scale system interactions. And so plate tectonics are incredibly important.
Because they explain why we see what we see in earth science. It's like gravity is to
physics. It's what evolution and natural selection are to biology. It really explains why we're
seeing what we're seeing. And what we're seeing is these massive plates that are sliding on
top of the mantle. And so you're sitting on the North America plate. And why do we have
the San Andreas fault here in California? It's because one plate is sliding past another.
And as we're forming new oceanic crusts, that's where we're going to have volcanoes in Iceland.
And why we're going to have so many earthquakes in Japan. It's all due to plate tectonics.
And there's a lot of evidence that shows this theory is correct. One piece of evidence is
that we're finding earthquakes along the margins of the plates. And so if you take a picture
of where all of the earthquakes have been. This is from 1963 to 1998, we're going to
see that it matches up perfectly with where the plates are going to be found. It's also
written in new rocks that are being formed. And we're creating new at these mid-Atlantic
ridges, or excuse me, mid-oceanic ridges. And so as these new rocks are being formed,
the magnetic poles are actually being written in the rock. And the pole on our planet switches
back and forth. And as it does that it's going to be written in the rocks. And so we can
see as this new rock is spreading out from the center, we can see the polarity in the
rock. And then things sitting on the plates are actually going to push down on them. Things
like massive glaciers and lakes are actually going to push down on these plates. And as
those glaciers go away, the earth is going to rebound. And so there's overwhelming evidence
that plate tectonics is correct. And so what's really going on here is that we have this
upper part of the mantle and the crust. And that's called the lithosphere. And those things
are made up or making up what are called the plates. And these plates are sliding and jostling
on this mantel. And as that mantel moves and as it heats up and cools down that's where
we get this motion from. And so this is kind of a picture of what this mantle looks like.
We're going to have areas where it's moving up. It's being heated up. And there are going
to be areas where it's cooling down. And as it cools down it's going to actually be moving
down. And so as it does that, imagine some plates on top of this mantel. They're going
to be shifted on that surface. So some places we're going to get movement away from, plates
away from each other. Sometimes towards each other. And sometimes passed one another. And
so what we start to see are all these earth science phenomena on our planet. And so if
we look in the middle of the ocean, what are we getting? Two oceanic plates that are actually
moving apart. And we're forming new rock right here in the middle. What happens if we have
two plates moving apart and it's on a continent and we get a rift valley? And sometimes we'll
have an oceanic plate sliding underneath one. So this would be like the Pacific plate sliding
underneath the North American plate. And we're going to have volcanoes, like Mount Saint
Helens right here. And the building up of new land. We're going to have the same thing
when we get these island arcs. We might have that off of the coast of Alaska. And so everything
can be explained by these plates and where these plates are interacting with one another.
But remember history is constantly being rewritten. And so these plates continue to move. Continue
to slide. And so new formations are occurring over time. So how do we help our students
with this? Well in the lower elementary grades we want to start with maps. And giving them
an understanding of how maps can be used. They could show us where land exists and where
water exists. And where water and land exist it's going to break that rock down into sand
and eventually soil. And we're going to find a lot of plants and animals at those margins
between the hydrosphere and the geosphere. As they move into the upper elementary grades
we want to start looking about landforms and patterns of landforms on our planet. And so
we tend to find mountains in the same area. We find them in the middle of a continent
or near the edges. And so we'll have continents or excuse me, mountains like the Rocky Mountains
that go all the way down this margin and all the way down South America as well. So they're
going to be patterns on where we find mountains. There are going to be patterns on where we
find earthquakes. When I taught earth science that's one thing that I used to have kids
do, is just plot where the earthquakes, the major earthquakes are happening each day.
Because there are going to be earthquakes every day and finding where those patterns
are. And where are the volcanoes on our planet? Where are we going to have these trenches
in our oceans? These deep places like the Mariana's Trench? And here are we going to
find these ridges in the ocean? This is a mid-Atlantic ridge right down here, down the
middle of the Atlantic Ocean. The Atlantic Ocean. And that crust is being formed. And
the Atlantic Ocean is going to get larger and larger over time. And we get into middle
school then we should start talking about this idea of plate tectonics. That we have
these plates. And those predict or excuse me, are predicted by where we see those earthquakes
and those volcanoes. There's a lot of evidence we have that these plates have been moving,
continue to move. And as far as continents go, that they were once one part of a supercontinent
called Pangaea. What would be some evidence that South America and Africa fit together?
I mean they sure fit together like a puzzle piece. But we find fossils on one that match
up with fossils on another. So it's huge pieces of evidence that these are moving and were
connected at one time. What's driving all of this is going to be motions within the
mantel, which is going to be this somewhat solid somewhat liquid part of our earth underneath
the lithosphere. So what's causing all of this heat? It's going to be radioactive decay
from the inside. From the core of our earth. It's heating it up. And as that mantel moves
up, it's pushing the plates on its surface. And as it cools down near the surface of our
planet, as that moves down we're also getting motion there. And so all of this is creating
plate tectonics on the surface. And that plate tectonics on the surface is creating those
landforms that we see. But remember those are being rewritten everyday. It occurs very
very slowly. Sometimes quickly. And I hope that was helpful.