GEOLOGY
Interested in learning a little bit about the earth?
Well, let's start at the beginning, the very beginning!
The genesis of the Earth
Most researchers currently believe that the earth formed via a process called cold accretion about 4.6 billion years ago.
This means that the earth was originally a collection of gas and dust particles that were condensed together by gravitational forces,
literally pulled together and compacted into a sphere by gravity. The primitive planet was very much different then it is today. There was no atmosphere, the surface
was molten, there were no seas, and life was still a billion or so years away.
As the earth cooled it began to take a shape that would be recognizable today. Atmospheric gases and water were either vented by volcanoes, or brought in when comets collided
with the planet. As the crust cooled and hardened forces within the earth began to arrange the surface of the earth into large moving plates. The movement of these plates against one another
generated the landforms that we know today, such as mountains and ocean basins. The interaction of these plates and their effects on the surface are known as plate tectonics.
It was about 3.5 billion years ago that the first forms of life originated on the earth, these early life forms were very primative bacteria and algae. However they laid the genetic framework upon which all future
life would evolve.
Evolution of life
The earliest life forms persisted virtually unchanged for nearly 3 billion years. Then, a little less then a billion years ago, things began a dramatic change. Life began evolving into multicellular
forms and body styles began differing from one another.
For the first time organisms that we would recognize began to take form. By 600 million years ago, all of the basic phyla that exist now had evolved. Life at this time was concentrated in the seas. There were
reef building creatures, crawling and free swimming creatures,
predators and prey. For about the next 300 million years sea life went through explosive phases of evolution and change. It was during this time that life began its first forays onto land.
At about 240 million years ago those early land dwellers began some explosive
evolution of their own. The age of dinosaurs had begun. Dinosaurs ruled the earth up until 66 million years ago, at which time mammals began evolving into forms that persist until today. The earliest
hominids (man like) evolved about 2-3 million years ago.
The world beneath our feet
The earth is made up of a combination of elements that form
minerals that form the very
rocks we are standing on. The core
of the earth is composed of molten hot nickel and iron. As you approach
the surface from the core you pass through the mantle which is made of iron
and magnesium rich silicate minerals.
Finally as you reach the surface you will find it is made up of
rocks rich in silicon and lighter elements.
The most common minerals at the surface are feldspars, quartz, micas,
carbonates, and a few other less common minerals . These minerals
combine to form rocks. There are three primary types of rocks that make
up the surface of the earth.
The first type are the igneous rocks, which are formed by the cooling of
volcanic materials and magma. Examples of these are granites and basalts. Secondly
are the sedimenary rocks, these are formed from
particles of other rocks that are compacted and
cemented together. Examples include sandstones, limestones, and shales.
The third type of rocks are the metamorphic rocks, these are formed when other rock
types are subjected to extreme pressure and/or temperature. This causes them to change
in form, examples are slates and marbles.
The science of Geology
Geology is a very broad field that touches on many subjects. You can study the history of
past life (paleontology), or the effects of erthquakes on present life (seismology). A few
of the important fields of study
in geology are given here. Mineralogy is the study of the nature, properties, and identification
of various minerals.
Stratigraphy and sedimentation deals with the laying down of sedimentary rocks and the interpretation
of the environments under which they developed. Structural geology is the study of the forces that shape
the earth, the folds, faults, bending, and breaking of the earths surface. Petrology is the study of
rocks under a microscope.
Hydrology is the study of groundwater and its relation to rocks around it. Geomorphology is the study
of landforms, weathering, and why the land around us looks the way it does. Geologist have to use physics,
chemistry, math, engineering, and computer skills, along with many other disiplines.
Careers
There are many career opportunities available for a geologist approaching the next mileneum. Nearly every resource utilized by
mankind comes from the earth and it is the job of the geologist to make sure they are extracted efficiently,
safely, and in an enviromentally sound way. Geologists work on the recovery of petroleum, on the mining
of metals and ores, the management of waterways, and the protection of the environment. Geologists are employed
by oil companies, state and federal agencies, engieneering firms, and many others involved in the study and
management of earth resources.
If you have any geology, or earth science questions please e-mail me and Ill get an answer to you as soon as I can.
If its a good question, Ill post it along with your name on this page for a while.
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Email: whittin7@hotmail.com
