Earth Materials and Processes

The materials that make up the Earth are mainly rocks (including soil, sand, silt, dust) . Rocks in turn are composed of minerals. Minerals are composed of atoms,

Processes range from those that occur rapidly to those that occur slowly

Examples of slow processes
Formation of rocks
Chemical breakdown of rock to form soil (weathering)
Chemical cementation of sand grains together to form rock (diagenesis)
Recrystallization to rock to form a different rock (metamorphism)
Construction of mountain ranges (tectonism)
Erosion of mountain ranges

Examples of faster processes
Beach erosion during a storm.
Construction of a volcanic cone
Landslides (avalanches)
Dust Storms
mudflows
Processes such as these are constantly acting upon and within the Earth to change it. Many of these processes are cyclical in nature.



Rain comes from clouds - falls on surface, picks up sand, silt and clay, carries particles to river and into ocean. Water then evaporates to become clouds, which move over continents to rain again.


Most surface rocks started out as igneous rocks- rocks produced by crystallization from a liquid. When igneous rocks are exposed at the surface they are subject to weathering (chemical and mechanical processes that reduce rocks to particles). Erosion moves particles into rivers and oceans where they are deposited to become sedimentary rocks. Sedimentary rocks can be buried or pushed to deeper levels in the Earth, where changes in pressure and temperature cause them to become metamorphic rocks. At high temperatures metamorphic rocks may melt to become magmas. Magmas rise to the surface, crystallize to become igneous rocks and the processes starts over.

External Processes

Erosion- rocks are broken down (weathered) into small fragments which are then carried by wind, water, ice and gravity. External because erosion operates at the Earth's surface. The energy source for this process is solar and gravitational.

Internal Processes

Processes that produce magmas, volcanoes, earthquakes and build mountain ranges. Energy comes from the interior of the Earth, Most from radioactive decay - nuclear energy