Geology

Geology is the science of the earth which explains, among other things, earthquakes, volcanoes, and tsunamis; also minerals, rocks and rock formations and their ages.

The compositional geological divisions of the earth were understood decades before the development of the theory of plate tectonics - the idea that the earth’s surface consists of large plates that move. By the 1970s, however, geologists began to realize that the plates had to be thicker than just the crust, or they would break apart as they moved. In fact, plates consist of the crust acting together with the uppermost part of the mantle; this rigid layer is called the lithosphere and it ranges in thickness from about 10 to 200 km. Rigid lithospheric plates "float" on a partially molten layer called the aesthenosphere that flows like a very viscous fluid, like Silly Putty®. It is important to note that although the aesthenosphere can flow, it is not a liquid, and thus both S- and P-waves can travel through it. At a depth of 660 km, pressure becomes so great that the mantle can no longer flow, and this solid part of the mantle is called the mesosphere. The lithospheric mantle, aesthenosphere, and mesosphere all share the same composition (that of peridotite), but their mechanical properties are significantly different. Geologists often refer to the aesthenosphere as the jelly in between two pieces of bread: the lithosphere and mesosphere. For a discussion of Seismology, P and S waves

Go to SEISMOLOGY from GEOLOGY

For a beautiful poem about the earth and rocks go to

Go to Earth from GEOLOGY

Geology discusses the outer part of the earth: lithosphere, crust, mantle and asthenosphere. The outer shell of the earth, 50 to 100 km in depth is called the lithosphere. The lithosphere contains the crust and the upper mantle.This crust comes in two “flavors” ; the continental crust, about 35 km thick, lies under the continents. Under the oceans the crust is much thinner, only about 5 km thick. Below the crust is the mantle which extends downwards about 2900 km. Beneath the lithosphere and in the upper mantle lies the athenosphere which is hot, plastic and deformable. The lithosphere moves on the athenosphere.

Quakes and volcanoes involve the earth’s crust and most especially the tectonic plates which move slowly on the earth’s athenosphere. These huge plates can crash against each other and when both plates support continents, create huge mountains by compression. When one plate is oceanic and the other continental, the heavier oceanic crust subducts (dives below) the continental plate and produces volcanoes. When two oceanic plates move away from each other (tension) they produce a trench containing new ocean crust, and also produce quakes and volcanoes. Earthquakes are also produced by “Transform Faults” in which two plates slide past each other. The great 1906 San Francisco earthquake was a result of plates slipping along the San Andreas fault. Under-water earthquakes can produce extremely dangerous tsunamis.

http://pubs.usgs.gov/gip/dynamic/dynamic.html

Here is a unique and interesting site about evolution; give it a try! Go To Evolution

Here is an interesting educational site for kids about geology:

Every geologist, amateur or professional, needs good binoculars

Zhumell 20x80 SuperGiant Astronomical Binoculars Item# ZHUG003 List Price: $199.00 Sale Price: $99.98.

I bought a pair of these giant binoculars . They are a great buy! They fit on my tripod beautifully; They are exactly as advertized.They yield incredibly sharp images.

To Science is Exciting From Geology