Presentation on theme: "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."— Presentation transcript:
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 events 8/19/11
What is a Geological Timescale? A scale of the history of the earth, supported by geological/archeologi cal 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)