Geology is one of the few sciences that take into account the broad spectrum of "science."
- chemistry for the chemical makeup of rocks and hydrogeology, the study of groundwater
- physics for help in understanding processes like earthquakes and geological engineering associated with building roads and structures.
- biology for understanding fossils - everybody remembers Jurassic Park, right?
- math for modeling various systems
There have been many myths and legends through the years to explain the Earth's processes, from mythology to Aristotle to Native Indian folklore.
- During the 17th and 18th centuries, the popular theory was "Catastrophism" - a theory which explained the Earth's features by theorizing that the landscape as we see it today formed by a series of great catastrophes.
- things like the Grand Canyon, Niagra Falls, the Rockies, etc.
- As science matured, the "Principal of Uniformitarianism" evolved. This theory used present day physical laws that govern processes to explain the evolution of landforms in the past. "The present is the key to the past".
- Physical laws have remained constant through time, and landforms such as the Grand Canyon can easily form from physical processes governed by these physical laws given a sufficient amount of time. A long time.
The inner Earth:
Inner core: solid iron. 756 miles in diameter (1216 km)
Outer core: molten metallic layer of Ni and Fe about 1410 miles thick (2270 km)
Mantle: 82% of the Earth's volume. 1789 miles thick (2885 km). Composed of iron-magnesium rock. Subdivided into two zones:
Mesosphere: High pressure at this depth causes the mantle to be strong and rigid.
Asthenosphere: Hot weak zone in the mantle capable of flow. Like silly putty. This is caused by partial melting of the rocks as the temperature rises. This zone is about 200 km thick.
Lithosphere: Above the asthenosphere is the lithosphere, a zone a solid, hard rock which includes the upper mantle and the crust.
Crust: Light outer skin about 3 to 25 miles (5-40 km) thick. This is what we live on. Includes all the rock you see in the world today. The crust is divided into two parts: Continental and oceanic crust, & both are distinctly different. The key word here is LIGHT, because the crust basically "floats" on top of the mantle.