BR: D5 Draw a picture of the globe. Then, add and identify the following: The Equator The Prime Meridian The Tropic of Cancer The Tropic of Capricorn The Arctic Circle The Antarctic Circle, etc. Lines of Latitude Lines of Longitude

World Geography Ch. 2.1 Inside the Earth

The Earth and its Insides This is the crust; ~30-60 miles deep If we were to cut into the Earth, what might we find? What would it look like? It would look something like this: The outside is the crust, a thin, rocky shell that covers the planet’s surface. It has oceans, continents, or those giant land masses we know and love, etc. Below that is the mantle, a layer of hot dense rock. It has two layers: a lower, deeper solid part, while the upper (closer to the surface) part is liquid rock called magma. When a volcano erupts, we see this molten rock, magma, reach the surface (now known as lava). This is the mantle; ~1,750 miles thick Lava on the surface Magma in the ground

The Earth’s Insides, Part II This is the Outer Core; ~1400 miles thick! The Earth’s Insides, Part II Crust Below that is outer core, a hot, molten layer that we believe reaches an incredible 8,500°F! And now, we’ve reached the inner core, the center of the Earth! This is under incredible pressure, so much so that the iron and nickel that it is made up of is in a solid state. So how do we know all of this? We haven’t ever dug that deep, but science and observation has given us lots of clues: VID Mantle Here’s the Inner Core; ~1500 miles across.

Shaping the Earth’s Surface Forces acting both inside and outside the Earth work to change the appearance of the Earth’s surface.

A Changing World Our Earth’s crust in constantly changing, though it may take thousands if not millions of years to do so. Mountains rise, are worn down, seas appear and dry up, etc. The theory of plate tectonics does a good job of explaining a lot of the movement and change that has happened on our Earth’s crust. As you can see below, our continents rest on these large pieces of crust, called plates:

Plate Movement These plates move quite slowly, so the change is almost imperceptible to us people. This movement is called continental drift. The rate varies from 1-7 inches / year. So, over millions of years, this can be dramatic. Have you noticed how the East edge of South America seems to fit like a puzzle piece with the West coast of Africa? That’s because ~200 million years ago, they were together, then slowly spread apart to their positions today. Evidence: Sea Spreading In fact, not just these two continents, but all of the continents were once joined together, in a supercontinent scientists call Pangaea. The fossil record confirms this.

Plates Meet So while some plates are spreading, others are running into each other as well. This smashing together of plates creates mountain ranges, (like the Himalayas) and also leads to volcanic activity. This explains the so called “Ring of Fire” around the Pacific Ocean: VID To make room, and “recycle” the extra land that would otherwise exist, one plate will often end up going underneath another one. The oceanic plates are usually thinner and denser, so they’ll usually slide under the thicker continental plates. This is called subduction. The plate melts back into the mantle, and the newly created magma creates pressure, which pushes back up as volcanoes, or creates earthquakes as the plates suddenly and violently scrapes together. Earthquakes

Plates Meet, Part II Earthquakes are very common in areas where plates come together, for good reason. Sometimes the plates don’t meet head on, but they might slide past each other. This type of encounter will create faults, or cracks in the Earth’s crust. These areas are prone to earthquakes, as the plates scrape along each other. One of the most well known ones is the San Andreas Fault in California, which has led to many destructive earthquakes in the past, and will continue to do so. Locally, Utah also has the Wasatch Fault, which causes larger earthquakes, but less frequently. VID

Weathering & Erosion The crust is being affected by many other forces as well. Weathering is the breaking down of rock, by water, ice, chemicals and even plants. For example, as water works its way into cracks in rocks, then freezes (due to colder nights, etc.), it expands and cracks the rock further. This frost / ice wedging is just one example of weathering. Erosion happens when these broken rocks and sediments are picked up & moved to another place by ice, water or wind. This is easily seen with rivers. VID, Santarem River shows this sediment being carried.

HW Reminders: Remember, your guided notes from last chapter were due Friday. Get those turned in ASAP if you haven’t already!