The Rock and Fossil

Record

Chapter 15

Sections 1 - 5

Objectives – Page 123

CO: SWBAT describe how the science of geology has changed over the past 200 years.

LO: SWBAT explain how studying the Earth’s present reveals the story of Earth’s history.

Learning Objectives

Describe how the science of geology has changed over the past 200 years.

Interpret ways in which rocks, fossils, and ice cores record Earth’s geologic history

Vocabulary

Uniformitarianism Catastrophism Paleontology Relative dating Superposition Geologic column Unconformity Absolute dating Isotope Radioactive decay Radiometric dating Half-life

Fossil Trace fossil Mold Cast Index fossil Geologic time scale Eon Era Period Epoch Extinction

Bellringer

On page 123, draw two columns, labeling one “Slow Changes” and the other “Fast Changes.”

Place the following events under the correct heading.

EVENTS

Erosion

Baking cookies

Making a movie

Landslide

Plant growth

Rainstorm

Growing taller

Earthquakes

Global Warming

Burning a forest

Plate tectonics

Volcanic eruption

Gaining weight

Eating a meal

Island formation

Bulldozing land

Reading a book from start to finish

Watching a TV show

Think About This

The present is the key to the past.

–How can studying the present reveal the story of Earth’s history?

Uniformitarianism

Idea developed by James Hutton

Processes that we observe today do not change over time

• The next slide shows how Hutton developed the idea of uniformitarianism.

Uniformitarianism vs.

Catastrophism

Hutton’s theories sparked a scientific debate by suggesting the Earth was much older than a few thousand years, as previously thought.

A few thousand years was not enough time for the gradual geologic processes that Hutton described to have shaped the planet.

Controversy Continued

To explain Earth’s history, most scientists supported the principle of catastrophism.

Catastrophism is the principle that geologic change occurs suddenly.

Supporters of this theory thought that mountains, canyons, seas, and other features formed during rare, sudden events called catastrophes.

And the winner is …

Catastrophism was geology’s guiding principle until the work of geologist Charles Lyell caused people to reconsider uniformitarianism.

Lyell published Principles of Geology in the early 1830s. Armed with Hutton’s notes and new evidence of his own, Lyell successfully challenged the principle of catastrophism.

Modern Geology

During the late 20th century, scientists such as Stephen J. Gould challenged Lyell’s uniformitarianism. They believed that catastrophes occasionally play an important role in shaping Earth’s history.

Today, scientists realize that most geologic change is gradual and uniform, but catastrophes that cause geologic change have occurred during Earth’s long history.

Paleontology

The history of the Earth would be incomplete without knowledge of the organisms that have inhabited our planet and the conditions under which they lived.

The science involved with the study of past life is called paleontology.

Paleontologist study fossils, which are the remains of organisms preserved by geologic processes.

http://www.fossilmuseum.net/Education.htm

http://www.sdnhm.org/exhibits/mystery/interactives.html

Question

Which of the following words describes change according to the principle of uniformitarianism?

–Sudden

–Rare

–Global

–Gradual

Question

How has the science of geology changed?

–Once dominated by theory of catastrophism

–Replaced by uniformitarianism in 1800s

–Today, scientists recognize both theories playing a role in geologic history

Question

What is one example of a catastrophic change?

–Global climate change caused by an asteroid striking Earth

Question

Why is uniformitarianism considered to be the foundation of modern geology?

–Most geologic change is gradual and uniform rather than sudden and catastrophic.

Finally …

Can you give an example of a type of recent catastrophe?

–Hurricane Katrina

– Indonesian Tsunami

–World Trade Centers – Catastrophe or disaster – what’s the difference?

Assignment

Using a double bubble map, compare and contrast the principles of uniformitarianism and catastrophism.