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
http://www.ferrara.com/columbia/attivita/viaggi/arizona/scorcio%20grand%20canyon.jpg Some are much more gradual, but still dramatic!
Absolute Age – The Actual time of an event in Years Relative Age – The Order that events took place.
Families of Rocks IgneousSedimentaryMetamorphic 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://mahi.ucsd.edu/Gabi/erth10.dir/lava-fountain.jpeg http://www.southwestbirders.com/Hawaii_2002/lava%20flow%20i.jpg
http://www.gsfc.nasa.gov/gsfc/earth/pictures/co2/volcanom.jpghttp://www.gsfc.nasa.gov/gsfc/earth/pictures/co2/volcanom.jpg When lava is blown out of a volcano in small particles it is called volcanicash.
Rocks formed from lava or ash are called volcanic rocks. Basalt Obsidian http://images.google.ca/images?svnum=10&hl=en&lr=&q=obsidian http://z.about.com/d/geology/1/0/R/K/basalt.jpg
Plutonic Rock – From magma that has cooled and crystallized beneath Earth’s surface. Granite is plutonic http://www.vermontmarbleandgranite.com/granite/imggranite/g4013rosaporrino.jpg
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://comp.uark.edu/~sboss/seds02.jpg http://wrgis.wr.usgs.gov/docs/parks/mojave/oncolith255x212.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
Metamorphic rocks were once igneous or sedimentary. They have been changed by heat and pressure under the ground.
Geological Structures Fractures are cracks in a body of rock.-can be formed by water freezing, earthquakes etc. http://falcon.tamucc.edu/~peichhubl/Pages/Clinkermacro.jpg
http://geophysics.tau.ac.il/personal/shmulik/images/fault%20in%20Arava.jpghttp://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.
http://www2.nature.nps.gov/geology/usgsnps/klondike/mi8.2dikes240x247labeled.jpghttp://www2.nature.nps.gov/geology/usgsnps/klondike/mi8.2dikes240x247labeled.jpg Dikes are igneous rocks formed in rock fractures when magma is squeezed upward and later cools.
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