Dynamic EarthDynamic Earth

Class 4Class 4

19 January 200619 January 2006

Any Questions?Any Questions?

Today:Today:

Video:Video:Dating the EarthDating the Earth

Homework #1 is dueHomework #1 is due Homework #2 posted to websiteHomework #2 posted to website

Two stratigraphic sections along with an igneous (unit A) Two stratigraphic sections along with an igneous (unit A) and metamorphic (unit B) body are shown. The beds in and metamorphic (unit B) body are shown. The beds in the stratigraphic section are sedimentary in origin and are the stratigraphic section are sedimentary in origin and are right side up (not overturned). Use the principles that you right side up (not overturned). Use the principles that you have learned in class to unravel geologic history:have learned in class to unravel geologic history:

YoungestYoungest JJ II G (A)G (A) A (G)A (G) F (note unconformity)F (note unconformity) EE DD CC BB

OldestOldest

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

Geology in the Geology in the News: StardustNews: Stardust

January 15, 2006 Stardust completed 2.88 January 15, 2006 Stardust completed 2.88 billion mile journey to a comet and backbillion mile journey to a comet and back

Its mission – return interstellar dust particles to Its mission – return interstellar dust particles to EarthEarth First interplanetary probe from Earth flew deep into First interplanetary probe from Earth flew deep into

space and brought back bits of a cometspace and brought back bits of a comet First U.S. mission designed to return samples from First U.S. mission designed to return samples from

another Solar System body since the Apollo another Solar System body since the Apollo missions to the Moon in the 1960s and early 1970smissions to the Moon in the 1960s and early 1970s

Geology in the News: Geology in the News: StardustStardust

Astronomers think comets are the oldest, most Astronomers think comets are the oldest, most primitive bodies in the Solar Systemprimitive 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 Composed of materials leftover after the planets formed around the Sun

about 4.6 billion years ago.about 4.6 billion years ago. Comets probably contain remains of materials used in the Comets probably contain remains of materials used in the

earlier formation of the starsearlier formation of the stars Particles returned by Stardust might even be older than the SunParticles returned by Stardust might even be older than the Sun

Comets are thought to contain organic materials essential for Comets are thought to contain organic materials essential for the origin of lifethe origin of life They may hold volatile carbon-rich elements that could provide clues to They may hold volatile carbon-rich elements that could provide clues to

the nature of the basic elements of our Solar Systemthe nature of the basic elements of our Solar System Studying comets today may provide evidence that these so-Studying comets today may provide evidence that these so-

called dirty snowballs brought water to the Earth, making life called dirty snowballs brought water to the Earth, making life possiblepossible Studying the dust should shed light on the origin of the Solar System Studying the dust should shed light on the origin of the Solar System

(age of the Earth) and origins of life on Earth(age of the Earth) and origins of life on Earth

TTueuesdaysday Please read Chapter 2 in the textPlease read Chapter 2 in the text