1. Dynamic Earth Class 4 19 January 2006

2. Any Questions?

3. Today: Video: Dating the Earth Homework #1 is due Homework #1 is due Homework #2 posted to website Homework #2 posted to website

4. Two stratigraphic sections along with an igneous (unit A) and metamorphic (unit B) body are shown. The beds in the stratigraphic section are sedimentary in origin and are right side up (not overturned). Use the principles that you have learned in class to unravel geologic history: Two stratigraphic sections along with an igneous (unit A) and metamorphic (unit B) body are shown. The beds in the stratigraphic section are sedimentary in origin and are right side up (not overturned). Use the principles that you have learned in class to unravel geologic history: Youngest Youngest J I G (A) G (A) A (G) A (G) F (note unconformity) F (note unconformity) E D C B Oldest Oldest

5. What radioactive elements might you use to date an igneous rock that is approximately 1 billion years old? What radioactive elements might you use to date an igneous rock that is approximately 1 billion years old?

6. Geology in the News: Stardust January 15, 2006 Stardust completed 2.88 billion mile journey to a comet and back January 15, 2006 Stardust completed 2.88 billion mile journey to a comet and back Its mission – return interstellar dust particles to Earth Its mission – return interstellar dust particles to Earth First interplanetary probe from Earth flew deep into space and brought back bits of a comet First interplanetary probe from Earth flew deep into space and brought back bits of a comet First U.S. mission designed to return samples from another Solar System body since the Apollo missions to the Moon in the 1960s and early 1970s First U.S. mission designed to return samples from another Solar System body since the Apollo missions to the Moon in the 1960s and early 1970s

7. Geology in the News: Stardust Astronomers think comets are the oldest, most primitive bodies in the Solar System Astronomers think comets are the oldest, most primitive bodies in the Solar System Comets are frozen bodies of ice and dust Comets are frozen bodies of ice and dust Composed of materials leftover after the planets formed around the Sun about 4.6 billion years ago. Composed of materials leftover after the planets formed around the Sun about 4.6 billion years ago. Comets probably contain remains of materials used in the earlier formation of the stars Comets probably contain remains of materials used in the earlier formation of the stars Particles returned by Stardust might even be older than the Sun Particles returned by Stardust might even be older than the Sun Comets are thought to contain organic materials essential for the origin of life Comets are thought to contain organic materials essential for the origin of life They may hold volatile carbon-rich elements that could provide clues to the nature of the basic elements of our Solar System They may hold volatile carbon-rich elements that could provide clues to the nature of the basic elements of our Solar System Studying comets today may provide evidence that these so- called dirty snowballs brought water to the Earth, making life possible Studying comets today may provide evidence that these so- called dirty snowballs brought water to the Earth, making life possible Studying the dust should shed light on the origin of the Solar System (age of the Earth) and origins of life on Earth Studying the dust should shed light on the origin of the Solar System (age of the Earth) and origins of life on Earth

8. Tuesday Please read Chapter 2 in the text Please read Chapter 2 in the text