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.