Chapter 1 book f pg. 6 week 3 of term 2

Earths surface is constantly changing. It has been lifted up, pushed down, bent, broken, melted and turned into new rock, geology is the study of all of these process. geology: The science of dealing with the

physical nature and the history of the earth, including the structure of the crust, the composition of the interior, individual rock types, and the study of ancient life forms from fossil evidence.

How do we know what is inside the earth? Can we look ? The deepest hole in the earths

crust is a gold mine in South Africa and it is only 3.8 km deep we would have to go 1,600 times deeper to get to the center.

No, so how do we know what is down there. Remember the blocks we did at the first of the year We have evidence that we have used to make a good

educated guess. The two main types of evidence are.

Direct evidence : this is evidence that comes from rock samples.

Indirect evidence: this is the evidence that we get from seismic waves.

We have evidence from drilling 12 km into the crust, this gives us a good idea of the conditions at that depth and the conditions under which the rock was formed.

The other evidence comes from rocks that the earth its self has blasted to the surface from a deep a 100 km.

Seismic waves are made from earth quakes, we can measure the different types of waves and how they travel through different materials in the earth and different densities. Solids vs. liquid Dense vs. not dense

The crust The mantel The core

The crust: Rock that forms the outer most layer of the earth, like our skin. It covers the entire earth on dry land and on

the sea floor. It’s the thickest under mountains and the

thinnest beneath the ocean. It ranges on average from 5 to 40 km thick.

There are two main types of rock that the crust is made of.

Basalt: a dark igneous rock of a fine texture Granite: is usually a lighter igneous rock of a much more

coarse texture .

Mantle: a layer of rock just below the crust and above the core that is hot but solid. The mantle is around 3,000 km thick and is

has many different layers . There are two parts of the mantle that are

important to know. The lithosphere: this is the upper part of the mantle and

the crust together. The Asthenosphere: this is the lower soft part of the

mantle that the lithosphere floats on it is soft but still solid.

The core is below the crust and the mantel. Is has two parts, an outer core and an inner core. Core: the center of the earth made of

heavy metals mostly iron and nickel. The outer core is liquid or molten metal made

of iron and nickel. The inner core is also made of nickel and iron

but is solid. Because of the amount of pressure the atoms cant spread out and become a liquid.

What is the magnetic field? Magnetic field: an invisible field created by

the earths core that shields the earth from much of the suns harmful radiation.

It is created by the liquid molten metal rotating around the solid core creating a magnet. The convection currents also play and important part in this process.