Do Now 8/19/11 What observations did you make about the length of time that humans have existed vs. the length of time the earth has existed? How does human impact on the planet compare to other species impact on the planet?
Answer to DO NOW Humans are a miniscule amount of time in comparison to the entire history of the earth. Homo-sapiens are believed to appear 100,000 years ago, and the earth is 4.6 billion years old. In the very short amount of time we have been here though we have spread across the entire globe and made a bigger impact than any other species.
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)
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 (human genus) show up? About 6 million years ago.
What sort of impact have homo sapiens had on the earth? In the 100,000 years homo-sapiens have existed we have consumed resources in almost every part of the earth.
Will the earth survive? Will we?