Lecture 4

The Earth: LithosphereThe Earth: Lithosphere

The EarthThe Earth

Biosphere – living thingsLithosphere – land Atmosphere – air Hydrosphere - water Cryopshere - ice

http://www.icess.ucsb.edu/

LithosphereLithosphere

The solid portion of the earth Rocks and its different forms

Layers of the earthLayers of the earth

According to composition According to physical composition

According to CompositionAccording to Composition

Crust Outermost layer Continental and oceanic crusts

Continental crust – directly underneath the continents

Oceanic crust – landmass underneath the oceans

– seafloor

http://www.av1611.org/images/inside_earth.jpg

http://www.nvcc.edu/home/cbentley/scientific_illustration/earth_layers.jpg

According to CompositionAccording to CompositionMantle

- the layer next to the crustTrivia: the boundary between the crust and the

mantle is called Mohorovicic discontinuity

Core - made up of metallic ball (nickel and iron)

Trivia: the boundary between the core and the mantle is called Gutenberg discontinuity

According to Physical PropertiesAccording to Physical Properties Lithosphere

entire crust + uppermost mantle coolest layer of the earth cool and rigid

Athenosphere rocks are near their melting points this layer is flowing

Melting Point – the temperature at which an object melt

http://www2.sunysuffolk.edu/anastaj/OC%2015%20web%20page/Layers%20of%20Earth.jpg

According to Physical PropertiesAccording to Physical Properties

Low-velocity zone- seismic waves slow down when they

pass this region Mesosphere

- despite its high temperature, the rocks remained solid- very high pressure prevents rocks from melting

According to Physical PropertiesAccording to Physical Properties

In terms of physcial state, the core has twoparts: Outer Core

- Liquid portion of the core Inner core

- Metallic portion of the core

Movements in the earth Movements in the earth

Continental drift – movements of the continents

Seafloor Spreading – movements of the oceanic crust

Continental driftContinental drift

Alfred Wegner - proponent of the continental drift theory

Pangeae : when the continents were just oneland mass

Continental driftContinental drift

Alfred Wegner proposed that the continental crusts move

Adams, S. and Lambert, E. Earth Science: An Illustrated Guide To Science,2006. NY: Chelsea House

Evidences supporting continental drfitEvidences supporting continental drfit

Geographical evidencecontinents fit like a jigsaw puzzle

Adams, S. and Lambert, E. Earth Science: An Illustrated Guide To Science,2006. NY: Chelsea House

Evidences supporting continental drfitEvidences supporting continental drfit

Geological evidence- three old mountain zones traversing different continents

-rocks along the matching coastlines are similar

Evidences supporting continental drfitEvidences supporting continental drfit

Biological evidence- identical fossil of plants and animals were found in different continents

Evidences supporting continental drfitEvidences supporting continental drfit

Biological evidence- identical fossil of plants and animals were found in different continents

Seafloor SpreadingSeafloor Spreading

oceanic crusts are usually younger than continental crust

oceanic crusts are recycled

http://rst.gsfc.nasa.gov/Sect2/platespread.jpg

Plate tectonics theoryPlate tectonics theoryLithosphere are divided into plates which are in motion

movement is due to convection current

Convection current rising and sinking of rocks due to difference in

temperature hot temperature rocks rise and low temperature rocks

sink

http://www.geography-site.co.uk/pages/physical/earth/images/plates.gif

Natural TragediesNatural Tragedies

Volcanoes- opening in the ground where molten rock comes out.

Active Dormant Extinct

Natural TragediesNatural Tragedies

Earthquakes-due to movement of plate boundaries- Squeezing of rocks may cause breakage which

results to release of energy- Magnitude vs. Intensity

Seismic WavesSeismic Waves

Body waves – travel through the interior of the earth

1. Primary waves2. Secondary waves

Surface waves – reaches the surface of the earth and causes the earth to shake

1. Love waves2. Rayleigh waves http://s3.images.com/huge.96.481081.JPG

RocksRocks

Rock cycle

http://www.uwsp.edu/geo/faculty/ritter/images/lithosphere/rock_cycle.gif

Soil formationSoil formation

Weathering of rocks- breaking down of rocks into smaller pieces

Physical weathering- ice wedging, temperature changesand organic activity

Chemical weathering- oxidation, change in acidity and dissolution

Erosion -trasportation of weathered rocks

http://www.eoearth.org/articles/view/149767/

http://www.eoearth.org/articles/view/149767/

Superposition theorySuperposition theory

If the layers of rocks were left undisturbed, the age of the rock increases from top to bottom

Adams, S. and Lambert, E. Earth Science: An Illustrated Guide To Science,2006. NY: Chelsea House

How old is the earthHow old is the earth

Figure 2Adams and Lambert. Earth Science: An Illustrated Guide To Science, 2006. NY: Chelsea House

How old is the earthHow old is the earth

Adams and Lambert. Earth Science: An Illustrated Guide To Science, 2006. NY: Chelsea House

ReferencesReferences

• Adams and Lambert. Earth Science: An Illustrated Guide To Science, 2006. NY: Chelsea House

• Rabago, Lilia M., et al. Dynamic Science. 2003. QC: vibal Publishing House