Earth’s Interior

1.      The Science of Geology

Geology is the study of the planet Earth.

Modern geology began in the late 1700’s.

Geologists are scientists who study the forces that make and shape the planet.

            They study the chemical and physical characteristics of rock.

They map where different types of rock are found on and beneath the surface.

The describe landforms, the features formed in rock and soil by water, wind, and waves.

They have concluded that Earth’s landforms are the work of natural forces that slowly change the surface of Earth.

                        Studying Surface Changes

Geologists divide the forces that change the surface into two groups:

Constructive forces shape the surface by building up mountains and landmasses.

Destructive forces slowly wear away land masses.

            Waves, wind, rain, running water.

                                    Early observations in geology were simple.

Earth is a spherical with a 6000 km radius

It has 7 continents made of rock surrounded by oceans.

                        Geologists ask questions about earth and try to find the answers.

They use seismic waves to obtain indirect evidence that Earth is made up of several layers.

            Inside Earth


Cool: 0-20m beneath surface

For every 40m into the earth, add 1C. This increase continues for several kilometers.

After that, temperature increases more slowly, but steadily.


                                    Pressure increases with depth in the earth due to the weight of rock

                        Three main layers make up Earth’s interior:

                                    The Crust:

1.      Ranges in thickness of 5 to 40 km thick.

2.      The layer of rock that forms Earth’s outer skin.

3.      Contains rocks, mountains, soil, water.

4.      Comparatively very thin to other layers.

5.      Includes oceanic crust which commonly contains granite and basalt.

            Basalt is dark, dense, and has a fine texture.

Granite is light in color, has larger crystals than basalt, and is not as dense as basalt.

                                    The Mantle:

1.      Begins at a depth between 5 and 40 km.

2.      Layer of hot rock about 3000 km thick.

3.      The crust and the uppermost part of the mantle are very similar and form a rigid layer called the lithosphere.

a.       Litho <gr> means stone

b.      The lithosphere is about 100 km thick.

4.      Beneath the lithosphere, heat and pressure continue to increase causing the rock to become less rigid.

5.      The rock becomes pliable like hot tar and can bend.

6.      This soft layer is called the asthenosphere.

a.       Astheness <gr> means weak

7.      This layer can flow slowly.

The Core

                                                Earth’s core has an inner core and an outer core.

                                                            Outer Core:

Liquid iron and nickel that surrounds the inner core.

Despite the intense pressure, the outer core behaves like a thick liquid.

                                                            Inner Core:

A dense ball of solid metal due to the intense pressure.

                                    Earth’s Magnetic Field

Earths magnetic field is caused by the currents in the outer core.