Hi. It's Paul Andersen and this is disciplinary core idea ESS2A. It's on earth's
materials and systems. And as we look at the sphere of the earth itself, what we really
find is that there are four important spheres on our planet. First one in the geosphere.
That's going to be the stuff of the earth. It's going to be the crust that we live on,
but it's also going to be the mantle and the outer and inner core. What it's made up of.
On top of that we have what's called the hydrosphere. That's going to be the water. It's not only
going to be the liquid water, but the water that's as ice and water as a gas. It's also
going to be the rivers and the lakes and even the ground water. That's going to be the water
that's seeping down into the geosphere itself. On top of that we have the atmosphere. The
atmosphere is going to be all of the gases that are still held to our planet. But allow
us to do things like breathe and get nutrients. And then finally we have the biosphere. Biosphere
is going to really be at the interface of the other three spheres. It's where we can
get nutrients from the atmosphere and water and nutrients from the soil as well. And so
everywhere where life is on our planet is going to be the biosphere. And so what are
some important things you should understand? First of all energy is going to be delivered
to the earth primarily in the form of sunlight. And so we're going to utilize that energy.
And most of it is eventually going to be left as heat. But the matter of our planet is going
to be recycled over and over and over again. And so the water that you drink used to be
water that was in an ancient ocean. And it will be water that somebody else drinks millions
of years in the future. Now that's not totally true. We still get a little bit of matter
from space in the form of meteorites. And we lose a little bit of matter to space as
the gases are being lost into space. But primarily the matter is going to be recycled over and
over and over again. The rocks give us clues as to how the earth has changed over time.
There are three types of rocks. We've got igneous, sedimentary and metamorphic. But
these are constantly being turned in from one to another. And recycled over and over
again. So rocks are really the mantel that's cooled down to the point where we can live
upon it. And so if we look at where the geosphere, the atmosphere and the hydrosphere interface
with one another, all of those together create weather, which is going to be what it is like
today. Climate, what it is like over time. And then eventually the atmosphere and the
hydrosphere are going to start to breakdown that geosphere and we're going to get land
forms forming. We can also have land forms that are being created from energy within
the earth. But where does the biosphere exist? It's where all of these other three spheres
come together. You also have to understand that it's an incredibly dynamic place, the
earth. We have plates that are shifting on its surface. We have new crust that is being
created. We have crust that is being broken down. So it is an incredibly dynamic place.
So how do you teach all of this? Well in the lower elementary grades you want students
to understand that wind and water are important. They shape the earth. So they form the landforms
on our planet. And those landforms open up areas where the life forms or the living things
can exist. As they move into the upper elementary grades you want to start talking about these
four spheres. The geosphere, what the earth is made up of. The hydrosphere, where water
is. The gases of the atmosphere. And finally the biosphere. And the importance of all of
these interacting. And you could find no better place to see this than in the ocean itself.
So it's clearly the hydrosphere. But interfaces with the atmosphere. It's getting nutrients
from the geosphere. And it's filled with life. And that life is creating, for example all
of the cyanobacteria in the oceans are creating oxygen. Which is becoming part of the atmosphere.
And the carbon dioxide is changing the temperature which can impact the geosphere. And so we
have all these incredible interactions going on. As you get into middle school you want
to talk about how energy is utilized on the planet. That it's coming in, generally in
the from of sunlight. But we're also getting a lot of energy from the heat. So there's
a lot of leftover heat from the formation of the earth. But we also have radioactive
decay. And that heat on the inside is also being transferred to the surface of the planet.
We want to explain how matter is generally recycled over and over and over again. And
then you want to start talking about interactions on our planet. So interactions globally. And
interactions at the microscopic level. Small changes to our earth's surface. And massive
changes. And the idea that the time scale can change. We can have interactions on our
planet that occur really quickly, like a volcanic explosion or an earthquake. Or things that
can take billions of years, like plate tectonics and formation of new land forms. As you move
into high school you want students to understand that the earth is incredibly dynamic. And
those dynamics are built a part of feedback loops. So feedback loops are sometimes going
to keep our earth stable. And sometimes push it out of stability. But it's hard to understand
all of the feedback loops on our planet because it's incredibly complex. We want to talk about
the specifics of the geosphere. And how all of these plates are moving around. And how
they're sitting on top of what's called this mantle which is really almost like boiling
water. However it's just boiling rock or boiling earth. We can areas where it's moving up and
getting hotter. And eventually cooling down and sinking down in these convection currents.
And then we want to talk about climatic change. And how the earth is changing, not just day
to day, but year after year after year after year. And we can measure some of those. So
the ice ages over time are a piece of evidence that we use to show how it's changed over
time. But we can even look over millions of years. And so Pangaea was formed when all
of the continents came together to make this one gigantic super continent. And so again
the earth is dynamic. But it's the interface between these four spheres that's probably
the most important. And I hope that's helpful.