Do Now 8/19/11

• How does the existence of homo-sapiens (100,000 years ago) compare to the length of the earth? How does the impact humans have had on the earth compare to the impact of other species? Explain.

Geological Timescales and Catastrophic

events8/19/11

What is a Geological Timescale?

• A scale of the history of the earth, supported by geological/archeological evidence.

What are two ways that scientists can tell how old the earth is?

• Radiometric dating and Relative dating using fossils.

What is Relative Dating of Fossils?

• Using The law of superposition to compare ages of fossils.

What is radiometric dating?• The use of isotopes (like carbon 14)

to tell us the absolute date of a fossilized organism.

How do scientists divide the geologic timescale into eons,

eras and periods?

• By major events, such as extinctions.

What might cause a major extinction?

• A catastrophic event might cause a major extinction, like the dinosaurs.

What are some catastrophic events?

• Volcanoes• Earthquakes•Meteor showers• Severe temperature

changes (ice ages, global warming)

How old is the Earth?

• 4.6 billion years old.

When did the first signs of life show up?

• The first signs of life were 3.8 billion years ago.

When did the first homonoids show up?

• About 6 million years ago?

What sort of impact have homo sapiens had on the earth?

• In the 100,000 years homosapiens have existed we have consumed resources in almost every part of the earth.

Will the earth survive?