Time and Change & Rocks and Structures

The Earth is about 4.5 billion years old.

From: http://earth.geol.ksu.edu/sgao/g100/plots/1017_timeline.jpg

Humans have been here for a VERY small part of Earth’s history. How do we know the rest?

Some changes take place very quickly!

From http://www.em.gov.bc.ca/Mining/Geolsurv/Surficial/landslid/plate19.jpg

http://www.nhoem.state.nh.us/mitigation/Mt%20St%20Helens%20wo%20Frame.jpg

Some are much more gradual, but still dramatic!

http://www.ferrara.com/columbia/attivita/viaggi/arizona/scorcio%20grand%20canyon.jpg

Absolute Age – The Actual time of an event in Years

Relative Age – The Order that events took place.

Families of RocksIgneous

SedimentaryMetamorphic

Igneous – Were at one time in a hot, liquid state.

http://www.bishopmuseum.org/exhibits/pastExhibits/1997/treasures/large_images/LOIHI2.jpeg

Magma is molten rock that is underground

Magma

http://www.solarviews.com/raw/earth/earthfg2.gif

Molten rock on the surface of the earth is called lava.

http://www.southwestbirders.com/Hawaii_2002/lava%20flow%20i.jpg

http://mahi.ucsd.edu/Gabi/erth10.dir/lava-fountain.jpeg

When lava is blown out of a volcano in small particles it is called volcanic ash.

http://www.gsfc.nasa.gov/gsfc/earth/pictures/co2/volcanom.jpg

Rocks formed from lava or ash are called volcanic rocks.

BasaltObsidian

http://images.google.ca/images?svnum=10&hl=en&lr=&q=obsidianhttp://z.about.com/d/geology/1/0/R/K/basalt.jpg

Pumicehttp://www.gc.maricopa.edu/earthsci/imagearchive/floating_pumice_big.jpg

Plutonic Rock – From magma that has cooled and crystallized

beneath Earth’s surface.

http://www.vermontmarbleandgranite.com/granite/imggranite/g4013rosaporrino.jpg

Granite is plutonic

Solidifies as Plutonic Rock

http://www.uwsp.edu/geo/faculty/ritter/images/lithosphere/Earth_Structure/igenous%20landforms.jpg

When softer sedimentary rock is eroded, it will sometimes leave the harder plutonic rock formations.

http://wrgis.wr.usgs.gov/docs/parks/mojave/oncolith255x212.jpghttp://comp.uark.edu/~sboss/seds02.jpg

Sedimentary rock usually consists of rock fragments such as mud, sand or gravel that have been cemented together.

Weathering – the physical or chemical breakdown of rock exposed to water, wind or ice.

The particles resulting from weathering -carried by rivers to the sea floor-settle to form layers of sediment-become sedimentary rock

If plant or animal remains are buried, they may be preserved as fossils. http://www.fox.uwc.edu/fossils/wisc/protax1.jpg

A Leaf Fossil

http://www.dll-fossils.com/Images/ginkgoalesleaf-web.jpg

http://www.mineraltown.com/infocoleccionar/imatges/rock_cycle.jpg

Metamorphic rocks were once igneous or sedimentary. They have been changed by heat and pressure under the ground.

Shale (sedimentary) becomes Slate (metamorphic)

Geological Structures

http://falcon.tamucc.edu/~peichhubl/Pages/Clinkermacro.jpg

Fractures are cracks in a body of rock.-can be formed by water freezing, earthquakes etc.

http://geophysics.tau.ac.il/personal/shmulik/images/fault%20in%20Arava.jpg

A fault is a fracture along which there has been movement. Faults can be caused by earthquakes.

Dikes are igneous rocks formed in rock fractures when magma is squeezed upward and later cools.

http://www2.nature.nps.gov/geology/usgsnps/klondike/mi8.2dikes240x247labeled.jpg

http://www.indiana.edu/~geol116/week4/dike.jpg

http://www.geol.lsu.edu/henry/Geology3041/lectures/04IgneousStructures/4-22.gif

A dike at Shiprock New Mexico

http://www.gpc.edu/~janderso/images/folds.jpg

Folds occur when layers of sedimentary rock are squeezed and then buckle.

Erosion Surfaces -when rock has been exposed to weathering and erosion and later reburied, the boundary is rough and uneven. http://www.oldstoneage.com/montetwhite/kadarimages/profile%20photo.jpg

Strata – means there are layers.

http://www.labyrinth.net.au/~tdp/images/strata.jpg

Identify the structures in the diagrams on page 261 of the Text