A1 06 Earth

• Understand Earth’s interior: core (inner and outer), mantle, crust.

• Understand Earth’s geological features

• Understand Earth’s some of the Earth’s extinction events.

An attempt to answer the “big question”: what is out there?

Earth’s GeologyLACC: §7.2, 3, 4

1Wednesday, March 3, 2010

Earth’s Interior

http://earth.unh.edu/esci402/docs/Earth%20Interior.jpg




Earth’s Interior

http://physics.fortlewis.edu/Astronomy/astronomy%20today/CHAISSON/AT307/HTML/AT30703.HTM




Earth’s Interior

http://abyss.uoregon.edu/~js/ast221/lectures/lec13.html

Seismic waves travel at about 10 km/sec and, from mapping of the timing and type of wave around the globe, we are able to map the interior of the Earth. Changes in refraction of seismic waves are due to sharp changes in the density = discontinuities due to chemical composition.The result is that we know that the interior of the Earth has 4 components:

• a thin crust of density 3.3 gm/cc composed of metals, silicates (a substance called basalt)

• a semi-solid mantle of density 3.5 to 5.5 gm/cc composed of olivine Fe oxides

• a liquid outer core of density 9 to 11 gm/cc composed of molten Fe

• a solid inner core of density 17 gm/cc composed of Fe and Ni.




http://abyss.uoregon.edu/~js/glossary/basalt.html

http://abyss.uoregon.edu/~js/glossary/basalt.html

The Earth: Interior Heat

http://www.physorg.com/news62952904.html

the vast majority of the heat in Earth's interior—up to 90 percent—is fueled by the decaying of radioactive isotopes like Potassium 40, Uranium 238, 235, and Thorium 232....

A cross-section of the Earth reveals....

a thin, hard crust ranging from 10 to 100 kilometers thick....

a donut-shaped mantle 2,900 kilometers thick. Instead of dough, it consists of viscous molten rock that flows very slowly, on a geological time scale. "It moves about as fast as your fingernails grow," Marone explains....

a two-part core. "The inner part is about the size of our moon," Marone says, "and has a density of essentially steel." The outer core surrounding it is an ocean of liquid metal 2,300 kilometers thick.




The Earth: Tectonic PlatesEarth is the largest terrestrial planet; therefore, it is taking the longest to cool. It’s crust (Si, O, Fe, Al, Mg; 3 g/cm3) is broken up into >12 sections called tectonic plates which are floating on a convecting mantle.

The interior is hot due to (accretion, differentiation, and) radioactive decay.

Significant erosion keeps Earth’s surface young--a few hundred million years old. (The oldest rocks are 3.9 billion years old. All the planets formed 4.5 billion years ago.)


The Earth: Tectonic Plates

http://www.neiu.edu/~llsander/earthquakes.html

http://www.youtube.com/watch?v=QDqskltCixA 5:17The Early Earth and Plate Tectonics




http://www.youtube.com/watch?v=QDqskltCixA

http://www.youtube.com/watch?v=QDqskltCixA

Hot Spots

http://www.gasd.k12.pa.us/~dpompa/Mini%20Lecture.html

...the Hawaiian Island and the seamounts that extend from Hawaii to the Aleutian trench show the movement of the Pacific plate as it moved over the hot spot. Radiometric dating shows that the volcanic activity decreases in age toward the island of Hawaii, which is now over the hot spot.




The Earth: Impact Craters

http://www.unb.ca/passc/ImpactDatabase/CINameSort2.htm

Current total number of

confirmed impact structures: 176




The Earth: Arizona Impact

http://www.lpi.usra.edu/science/kiefer/Education/SSRG2-Craters/craterstructure.html

Photograph by David Roddy, United States Geological Survey.






Meteor Crater in Arizona is one of the best known examples of an impact crater on Earth. The crater is 1.2 kilometers (0.74 miles) in diameter and 200 meters deep. It formed approximately 49,000 years ago when an iron meteorite that was roughly the size of a school bus struck the Arizona desert east of what is now Flagstaff.





http://www.meteorcrater.com/eventsfun/exptheimp.htm

In a blinding flash, a huge iron-nickel meteorite or dense cluster of meteorites, estimated to have been about 150 feet across and weighing several hundred thousand tons, struck the rocky plain with an explosive force greater than twenty million tons of TNT (or around 1000 Hiroshima bombs). Traveling at supersonic speed, this impact generated immensely powerful shock waves in the meteorite, the rock and the surrounding atmosphere. In the air, shock waves swept across the level plain devastating all in the meteor's path for a radius of several miles.


http://www.meteorcrater.com/eventsfun/exptheimp.htm%60

http://www.meteorcrater.com/eventsfun/exptheimp.htm%60

Tunguska Blast

http://www.skyandtelescope.com/community/skyblog/newsblog/12662606.html

Trees near the Podkamennaya Tunguska River in Siberia still looked devastated nearly two decades after a large meteorite exploded above the ground in June 1908. The Tunguska event, which ranks as one of the most violent cosmic impacts of this century, leveled nearly 800 square miles of forested taiga.Smithsonian Institution




The Earth: Chicxulub

http://www.daviddarling.info/encyclopedia/C/Chicx.html

The Chicxulub Crater is believed to be the result of the collision with an asteroid measuring some 10 to 20 km across. The environmental effects that accompanied its formation were thought to have been responsible for the mass extinction at the end of the Cretaceous period, about 65 million years ago, in which the last of the dinosaurs, along with many other species, disappeared (see Cretaceous-Tertiary Boundary).

http://www.youtube.com/watch?v=5qJPTjMnwNk 2:25Chicxulub impact visualization




http://www.daviddarling.info/encyclopedia/A/asteroid.html

http://www.daviddarling.info/encyclopedia/A/asteroid.html

http://www.daviddarling.info/encyclopedia/M/mass_extinction.html

http://www.daviddarling.info/encyclopedia/M/mass_extinction.html

http://www.daviddarling.info/encyclopedia/C/Cretaceous.html

http://www.daviddarling.info/encyclopedia/C/Cretaceous.html

http://www.daviddarling.info/encyclopedia/D/dinosaur.html

http://www.daviddarling.info/encyclopedia/D/dinosaur.html

http://www.daviddarling.info/encyclopedia/C/Cretaceous-Tertiary_boundary.html

http://www.daviddarling.info/encyclopedia/C/Cretaceous-Tertiary_boundary.html

http://www.youtube.com/watch?v=5qJPTjMnwNk

http://www.youtube.com/watch?v=5qJPTjMnwNk

Ice Ages

http://deschutes.gso.uri.edu/~rutherfo/milankovitch.html

Milankovich cycles are cycles in the Earth's orbit that influence the amount of solar radiation striking different parts of the Earth at different times of year. They are named after a Serbian mathematician, Milutin Milankovitch, who explained how these orbital cycles cause the advance and retreat of the polar ice caps. Although they are named after Milankovitch, he was not the first to link orbital cycles to climate. Adhemar (1842) and Croll (1875) were two of the earliest.




Ice Ages

http://universe-review.ca/I09-15-iceages.jpg




Earth: Life?

http://www.answers.com/topic/extinction-intensity-png-1


http://www.sciencedaily.com/articles/i/impact_event.htm

http://www.sciencedaily.com/articles/i/impact_event.htm

Earth’s GeologyLACC: §7.2, 3, 4

• Understand Earth’s interior: core (iron; solid inner, liquid outer), mantle (rocky), crust; differentiation

• Understand Earth’s geological features: a few hundred million years old; plate tectonics and erosion (and a few hundred impact craters)

• Understand Earth’s some of the Earth’s extinction events: impacts (e.g. Chicxulub), Milankovich cycles

An attempt to answer the “big question”: what is out there?


LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe, 3rd ed.

• Ch. 7, pp. 171-172: #1.

Due at the beginning of next class period.

Be thinking about the Solar System Project.


Earth’s AtmosphereLACC §7.2, 3, 4

• Earth’s Atmosphere: composition, pressure, and temperature

• The Evolution of Earth’s Atmosphere

• Life on Earth

An attempt to answer the “big question”: where did we come from?


The Earth: The Atmosphere

• The greenhouse effect on Earth heats our planet by about 55°F.

• The Earth’s atmosphere (and magnetosphere) protect us from dangerous radiation and meteors.

• Earth’s surface temperature and pressure allow for liquid water on its surface!


The Earth: The Atmosphere

Composition

• N2 77%

• O2 21%

• Ar 1%

• H2O varies

• CO2 varies

1 bar surface pressure

59°F average surface temperature


Earth: Black Body Temperature

http://www.ldeo.columbia.edu/~kushnir/MPA-ENVP/Climate/lectures/energy/Radiative_Heat_Transfer.html

....Earth ... 255 K (-18 °C or

-0.5 °F). ...this would be the

temperature of the planet if it had no atmosphere.




Earth: The Greenhouse Effect

http://maps.grida.no/go/graphic/greenhouse-effect






[The] graphic [on the previous slide] explains how solar energy is absorbed by the earth's surface, causing the earth to warm and to emit infrared radiation. The greenhouse gases then trap the

infrared radiation, thus warming the atmosphere.





http://maps.grida.no/go/graphic/main-greenhouse-gases

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Earth: Atmospheric Evolution

http://www.fas.org/irp/imint/docs/rst/Sect19/Sect19_2a.html





http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/earth.htm

Materials for the atmosphere were brought to the earth by comets accreted during its formation, then released by volcanoes (From Don Dixon http://cosmographica.com/gallery/index.html). Additional late-arriving comets would have added additional material to the oceans and atmosphere.




http://cosmographica.com/gallery/index.html





http://ftp.astronomy.ohio-state.edu/~pogge/Ast161/Unit5/atmos.html

Origin of the Earth's AtmosphereAfter losing most of its original H and He, the Primordial Atmosphere of the Earth was built up by outgassing of the crust by volcanos:

• Mostly H2O and CO2

• Small amounts of N2 and sulfates • No oxygen (O2).

This is very different than our present atmosphere. How did our atmosphere get the way it did?





http://www.globalchange.umich.edu/gctext/Inquiries/Inquiries_by_Unit/Unit_8.htm





http://www.physast.uga.edu/~jss/1010/ch10/ovhd.html






Where did all the CO2 go?The primordial atmosphere had ~1000 times more CO2 than it does now. Where did it all go? • H2O condensed to form the oceans. • CO2 dissolved into the oceans and precipitated out as carbonates (e.g., limestone).Most of the present-day CO2 is locked up in crustal rocks and dissolved in the oceans.By contrast, N2 is chemically inactive • It stayed a gas in the atmosphere and become its dominant constituent.






Where did the O2 come from?The second major constituent of the present-day atmosphere is Oxygen (O2), but it was absent in the Primordial Atmosphere. Where did all the O2 come from?

• Molecular Oxygen (O2) comes primarily from photosynthesis in plants and algae.

• The O2 content of the atmosphere has increased from 1% to 21% during the past 600 Myr.

Ozone (O3):• Forms in stratosphere from O2 interacting with solar UV

photons.• Blocks UV photons from reaching the ground.

This made land life possible as solar UV radiation is hazardous to life.The presence of O2 and O3 in our atmosphere is a sign of life (photosynthesis).




Earth: Life?

• 3.9 billion years ago: chemical evidence of life

• 3.5 billion years ago: Stromatolite colonies

• 2 billion years ago: O2 accumulate is the atmosphere

• 65 million years ago: Chicxulub impact results in extinction of dinosaurs

• 200 thousand years ago: modern humans

• 1 hundred years ago: radio broadcasts


Earth: Life?


Colonies of trillions of these bacteria built up cabbage-like structures called stromatolites. The bulk of a stromatolite colony consists of layers of calcium

carbonate interspersed with mattes deposited by the cyanobacteria (which are photosynthetic). Stromatolites

still exist on Earth but are rare (mainly at two localities in Australia).




Earth: Climate Change

http://www.global-greenhouse-warming.com/ice-ages-and-sea-levels.html





http://www.windows.ucar.edu/tour/link=/earth/climate/medieval_warm_period.html&edu=high

The graph on the left, a reconstruction of average global temperatures over the past 1000 years, shows that during the Medieval Warm Period the temperatures were likely similar to the first part of the 20th century, climate cooled during the Little Ice Age, and has warmed dramatically in recent decades. Temperatures during the Medieval Warm Period were likely cooler than the temperature has been for the past few decades.

The Medieval Warm Period was a time of warm climate in Europe, the height of which was from about 950 until 1100 A.D. The warm climate overlaps with a time of high solar activity called the Medieval Maximum. The Medieval Warm Period occurred before the Little Ice Age (1350-1850 A.D.), a time of particularly cool climate in Europe and other places around the world.




http://www.windows.ucar.edu/tour/link=/earth/climate/little_ice_age.html&edu=high







http://www.climate4you.com/GlobalTemperatures.htm#Comparing%20global%20temperature%20estimates

All five global temperature estimates presently show stagnation, at least since 2002. There has been no increase in global air temperature since 1998, which was affected by

the oceanographic El Niño event. This does not exclude the possibility that global temperatures will begin to increase again later. On the other hand, it also remain a possibility that Earth just now is passing a temperature peak, and that global temperatures will begin to decrease within the coming 5-10 years. Only time will show which of these possibilities is the correct.


http://www.climate4you.com/GlobalTemperatures.htm




Earth’s AtmosphereLACC §7.2, 3, 4

• Earth’s Atmosphere: composition (N2, O2), pressure (1 bar), and temperature (59 °F), the greenhouse effect

• The Evolution of Earth’s Atmosphere: volcanic outgassing, comet impacts, thermal escape.

• Life on Earth: earliest fossils, O2 levels, climate change

An attempt to answer the “big question”: where did we come from?


• Ch. 7, pp. 171-172: #5.

• Ch 8: Tutorial Quizzes accessible from: http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M20b&product_isbn_issn=9780495017899&discipline_number=19

Due at the beginning of the next class period.

Be thinking about the Solar System Project.

LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe, 3rd ed.


http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M20b&product_isbn_issn=9780495017899&discipline_number=19






A1 06 Earth

Education

Transcript of A1 06 Earth