HMH Unit 1 Lesson 6

Geo=earth and Sphere=ball

The geosphere consists of four main layers: The crust, the mantle, the outer core and the inner core.

Earth's crust is the top layer of the geosphere.

It is solid and ranges in depth from 0 km to 70 km at the top of some mountains.

It covers Earth's surface.

Temperatures can range from 0° C to nearly 800° C close to the mantle.

The mantle is below the crust and divided into an upper layer and a lower layer.

The mantle consists of rock that is solid but can flow, and is about 2,900 km thick.

Away from boundaries with other layers, the mantle has a temperature of 1,350° C to 2,500° C

The outer core is below the mantle, from about 2,900 km to 5,200 km deep.

It is a liquid alloy made up mostly of iron and nickel, with a temperature of 4,000-5,500° C.

The inner core is at the center of Earth.

It is a solid ball of mostly iron and nickel.

It is 5,200 km to 6,400 km below Earth's surface and reaches temperatures between 5,500°C and 6,200°C.

You may have noticed that the geosphere changes.

 Rocks are broken down and moved by wind and water, changing the appearance of Earth’s surface. 

Changes that you can’t see also occur below Earth’s surface.

Study the dirt in the photo. What do you think dirt is made of?

If you look closely, you can see that dirt is made of specifically defined particles of sand, silt, and gravel, as well as other organic materials.

People often use the word dirt to refer to the material that is on the ground and that plants grow in, but the more accurate term is soil.

Soil is the top layer of Earth's crust and is made up of rock particles, clay and organic material.

The organic material consists of both living organisms and the remains of once-living organisms.

Soil is what plants grow in.

The rock cycle is a cycle in which rocks change from one form to another through natural processes.

Rocks are always changing

Some processes in the rock cycle happen more quickly than others.

Some, such as weathering and erosion, happen at Earth's surface while others, such as heat and pressure happen deep inside the Earth.

Igneous Rock is formed as magma cools.

It can be broken down into sediment by weathering and erosion.

It can also melt back into magma when exposed to high temperatures or change into metamorphic rock when exposed to high temperatures and pressure.

Sedimentary rock forms when sediment is compacted under moderates pressure and exposed to mineral-rich water.

It changes into metamorphic rock when exposed to hear and high pressures and can be broken down into sediment through weathering and erosion.

Metamorphic rock can be broken down into sediment through the processes of weathering and erosion.

If exposed to high temperatures, it can melt and then cool and become igneous rock.