Geological Time Scales
The earths geology has successional layers of different types of rocks, piled
on top of each other. Many of the common rocks looked at by scientists are
sedimentary rocks and extrusive igneous rocks (lavas, volcanic ash, and molten
rocks that have hardened on the earths surface). Layers of rocks are called
strata. The study of strata is called stratigraphy. In a vertical direction
of sedimentary or volcanic rocks, the rocks that are higher up are older than
the rocks under it. Rock layers were also close to horizontal. A rock unit goes
laterally unless there is something in its way to make it move.
The principle of
cross cutting relationships can be used to find out the way the rocks does what
it does. Simple ways to figure out geological time scales
have been around
since the early 1700s, and by the early 1800s, geologists have figured out
that many things that are the same were around in different parts of the world.
One of the earliest time scales was strata based on rock types in Europe.
When geologists made the earths geologic history in the 1700s and early 1800s,
they found out that the where the fossils were found was not just anywhere.
The fossils they found were in the same order. For example trilobites were
found lower than the tings that live in the water. Dinosaurs were found after
plants, bugs, and other reptiles. When a geologist gets a rock sample for
radiometric age dating there are
constraints on the age of the
information the geologist gets.
Lisa Andrew and Doug's Project
Fossil Evidence that
illustrates how life forms
evolve
Techniques used to
determine geological time
scales
techniques used to learn
about the earth
Impact of Earthquakes
on the Enviroment
Factors responsible for
Earthquakes
Factors responsible for
mountain building
Factors Responsible for
Ocean Ridges
Factors Responsible for
Volcanic Eruptions
Theory of Plate
Tectonics
Impact of Volcanoes
on The Enviroment
Bibliography
