WednesdayNovember 17, 2010(Brief History of Geology; Relative Dating – Law of
Superposition; Project – Killer Earthquakes)
The Launch PadWednesday, 11/17/10
What are the two major mechanisms that drive plate motion?
Older, denser, heavier plates subduct and pull the plates along with them. The
buoyant magma at the elevated ridges pushes the plates apart.Mantle plumes extend upward from the
mantle - core boundary and cause convection within the mantle, which adds
to the motion of the plates.
Announcements• Don’t come to school
next week.
Assignment Currently Open Pages Date of Notes
on Website Date Issued Date Due
Five Multiple Choice Questions
on Plate Tectonics
11/11 11/12
Project – Decade Volcanoes 11/15 11/19
A Brief History of GeologyDuring the seventeenth and
eighteenth centuries, the doctrine of catastrophism
strongly influenced people’s thinking about Earth.
Catastrophists believed that Earth’s landscapes had been developed primarily by great
catastrophes. James Ussher, in the mid-1600s,
concluded that the Earth was only a few thousand years old, having been created in 4004
B.C.
A Brief History of Geology
Modern geology began in the late 1700s, when
James Hutton, a Scottish physician, published his
Theory of the Earth.
Hutton put forth a fundamental principle
that is a pillar of geology today: uniformitarianism.
A Brief History of GeologyThis principle simply states that the
physical, chemical, and biological laws that operate today have also
operated in the geologic past.
This means that the forces and processed that we observe
presently shaping our planet have been at work for a very long time.
This idea is commonly expressed as “The present is the key to the past.”
Determining Age• How old someone or something is can be thought of in
two different ways: relatively or numerically.• For instance, consider these two scenarios:
– Frank is older than John, and John is older than Mary.– Frank is 18 years old, John is 16, and Mary is 10.
• The first statement is relative; it lists the order of the ages, but doesn’t provide actual numerical information.
• The second statement is numerical, as it gives the actual ages of the three.
• Geologists use both relative and numerical dating when accessing the age of rocks and formations.
Relative Dating Relative dating means
placing rocks in their proper sequence of formation.
This technique cannot tell us how long ago something
took place, only that events took place one after the
other.
Again this is not a numerical dating procedure!
Relative Dating Principles and rules of relative dating:
The Law of Superposition states that in an undeformed sequence of sedimentary
rocks, each bed is older than the one above it and younger than the one below.
In other words, the oldest rocks are on the bottom and the youngest on the top.
Superposition is Well Illustrated in the Grand Canyon
Figure 11.3
ProjectKiller Earthquakes
Research the 10 most devastating earthquakes of all time.
You must include the following information on each quake:
epicenter location, affected areas, date, Richter Scale magnitude,
tsunamis (if applicable), death toll, monetary loss
You can do this on a sheet of paper, or electronically using Open Office Writer or
Impress (send this to my email).Extra credit will be given for illustrations.