Earth Materials and Landforms:
Earth Structure

Introduction

Little direct evidence has been gathered about the interior of the Earth. Most of what we know has been gleaned from materials brought to the surface as lava and the behavior of seismic waves propagated through the Earth. What we do know is that the Earth's interior is like a concentric series of layers progressing from the dense and intensely hot inner core toward the brittle outer shell of the crust. The objective of this lecture is to give you a fundamental background concerning the nature of the inner structure of the Earth and how it relates to what physical geographers study at the surface.

Interior Structure

Core

Inner Core- solid iron
Outer Core - molten metallic iron

Mantle

Represents 80% of the earth's total volume
Divided into upper and lower mantle
Material of the lower mantle has probably never been at the Earth's surface.
Upper mantle divided into three fairly distinct layers
- Upper mantle - rigid cooler layer (part of what's called the "lithosphere").
- Asthenosphere - plastic layer; contains pockets of increased heat from radioactive decay; susceptible to slow convection; least rigid portion of the mantle;
- Below asthenosphere - rest of the upper mantle-composed of rigid, solid rock material.

Lithosphere and Crust

Lithosphere contains entire crust and upper mantle to a depth of 43 mi (70 km)
Crust is fractured into many crustal plates.
- Continental crust and oceanic crust are different in composition and density. Continental crust is basically granite - high silica, aluminum (sial)
- Oceanic crust - basalt - high silica, magnesium (sima)
Lighter, less dense crust "floats" on the denser layers beneath.

crust.jpg (21225 bytes)

Can you ...

Describe the interior structure of the earth?

Describe the main components of oceanic and continental crust?

Describe the basic rock types that compose the oceanic and continental crust?

On to Minerals and Rocks