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Main Menu The Earth’s Crust The Earth’s Mantle The Earth’s Core Questions Dig Deeper With These Links

What We Will Learn The four layers of the Earth The crust The mantle The outer core The inner core

The Earth’s Crust The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 3-5 miles thick under the oceans (oceanic crust) and about 25 miles thick under the continents (continental crust). The Earth's surface is composed mostly of water, basalt, and granite. Oceans cover about 70% of Earth's surface.

The Crust Hey, did those Continents fit together at one time? The Earth’s crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle. CONTINETAL DRIFT The plates are made of rock and drift all over the globe; they move both horizontally (sideways) and vertically (up and down). Click Main Menu

The Earth’s Mantle The mantle is made up of rock materials and is sandwiched between the core and the crust. It consists of mainly solid rocks, but the upper mantle (closer to the crust) is actually a layer of semi-liquid molten rock called magma. This magma flows slowly underneath the crust like plastic (think of silly putty). The mantle makes up most of our Earth! Magma flows in upper part of mantle. This causes plates to move (plate tectonics).

Convection Scientists believe convection currents are what cause earth’s plates to move.  A convection current is caused by differences in temperature.  When a pot of water starts to boil, the water is hotter near the bottom, close to where the heat source is located.  Hotter water is less dense, and so it rises to the top.  The cooler water on top sinks to the bottom. This is a kind of convection current.

Convection in the Mantle The same type of current moves magma in the mantle of the Earth.  This is a continuous circular motion!

The Earth’s Outer Core The third layer of the earth is underneath the mantle, known as the liquid outer core. It is made mostly of the metal iron. The heat is so intense that the metals are molten, and the layer flows very slowly, generating energy that produces the magnetic field of the earth.

Earth’s Inner Core The temperature of the inner core is hotter than the Sun's surface! Therefore, the intense heat from the inner core causes material in the molten outer core and mantle to move around. Unlike the outer core, the inner core is solid! Click Main Menu

What Have We Learned? The Earth’s crust is pretty thin and is where we live. The Earth’s mantle is the largest part of our Earth. The upper part of the mantle moves slowly (kind of like squeezing silly putty) because of magma. Convection is the cycle of heat rising, falling as it cools, and then heating and rising again. We live on plates that are constantly moving! The outer core is liquid, and it produces our magnetic field. The inner core is solid and is hotter than the sun.

Time to Show Off! No…it would be too hot!!! You are so smart! So, Can we dig to China? Which layer makes up most of our Earth? Which part of the Earth is hotter than the sun? What is the source of our magnetic field? Does heat rise or sink? What happens after it cools again? What is the thinnest layer of the Earth? Click Main Menu

Answers Which layer makes up most of our Earth? mantle Which part of the Earth is hotter than the sun? inner core What is the source of our magnetic field? Because the outer core contains iron, when it flows it generates a magnetic field. During convection does heat rise or sink? What happens after it cools again? Heat rises and as it cools it sinks back down where it is heated again causing the cycle to repeat. What is the thinnest layer of the Earth? crust Click Main Menu

Dig Deeper With These Links Inside the Earth - label the Earth’s structures. Structure of the Earth - features a globe with a removable section. Science Odyssey: You Try It: Plate Tectonics - A hands-on exercise about plate tectonics and earthquakes from PBS. (requires Shockwave plug-in) Click Main Menu