How Do They Know?Earth’s Interior

The earlier views of the earth’s processes

were viewed by the catastrophic events, and related to gods. Poseidon was the god of earthquakes Zeus was the weather god Vulcan was the god of volcanoes Earth’s interior was the house of Hades

Historical Views

It has become determined that the earth is an

oblique spheroid. It processes a dipolar magnetic field. The Earth has a crust with an interior that is

composed of different layers The interior core has a source of heat.

Over Time

The direct evidence of what lies below our feet is

quite limited. Direct evidence refers to actual sample of Earth

materials from which composition and density of a certain area of the Earth’s interior can be determined.

The sources Drilling Inclusions in igneous rocks Roots of mountains Kimberlite pipes

The Evidence

Diamond drill bits have been bored into rock

and the cores have been brought to the earth surface.

This technique is limited as the material of the Earth increases in temperature with depth, (called a geothermal gradient) approximately 25ºC per kilometer.

Deepest drill hole to date is 12 km deep, located north of the Arctic Circle in Russia

Drilling

During magmas’ travel to the Earth’s surface

pieces of country rock, called inclusions. With uplifting and erosion at the Earth’s

surface the inclusion can provide information about the composition of the Earth at the depth the magma originated

Inclusions

Inclusions

Think of mountain being like an iceberg. To

have a high elevation a deep portion or root is needed to balance the structure.

As a mountain erodes over time the deep root of the mountain becomes uplifted and the root is exposed giving direct information about the interior. These depths can be up to 50km

Mountain Roots

Mountain Roots

Kimberlite pipes are a special intrusive

igneous rock formation which develop at great depths (around 600 km) below the surface. These then move upward to the surface.

They are sources of most of the world’s natural diamonds, but they also give clues as to the Earth’s interior.

Kimberlite Pipes

Kimberlite Pipe

One must remember that the Earth’s radius is

over 6300 km, and with direct methods of evidence only going to a depth of maybe 600 km, then much information about the interior is lacking.

To gather the information needed about the interior, indirect methods must be used. Of these most commonly used is seismology. The study of earthquakes

Overal