Plate Tectonics and Geology

Genesis of Earth Earth is 4.6 billion years old.  Same age as all other planets and the sun. Earth formation.  Nebular hypothesis. Diffuse cloud of matter rotating in space, formed a disk shaped body, which later formed into sun and planets. Planets are cooled and condensed gases that surrounded the sun.

Core Development  Earth was a homogeneous planet immediately after formation  But then, a profound reorganization as Earth initially heated up due to collision with other rocky bodies heat of compression Radioactive decay of elements  Earth heated up such that much of the interior melted causing dense elements like iron and nickel to sink to the core lighter elements like silicon and aluminum float to the crust Resulted in a stratified Earth - core, mantle, crust

Distribution of Elements  More than 100 elements in entire Earth, but 99% of Earth's mass is made up of only 8 elements Whole Earth:  Fe>O>Si>Mg>Ni>S>Ca>Al (others constitute < 1%) Earth's crust  O>Si>Al>Fe>Mg>Ca>K>Na (other constitute <1%)

Composition of Earth’s Crust Earth’s Crust Oxygen 46.6% Silicon 27.7% All others 1.5% Magnesium 2.1% Potassium 2.6% Sodium 2.8% Calcium 3.6% Iron 5.0% Aluminum 8.1% Fig. 10.4, p. 213

Layers of the Earth  Crust The surface of the Earth is a very thin layer made of rocks, minerals and clay We live on the crust of the earth crust

Layers of the Earth  Mantle- Upper and Lower The mantle is the biggest part of the earth; the magma is rich in iron and magnesium Convection occurs here and is thought to drive plate tectonics mantle crust

Layers of the Earth crust mantle Outer core Outer CoreOuter Core The outer core consists of molten iron and magmaThe outer core consists of molten iron and magma The outer core rotates giving the Earth a magnetic fieldThe outer core rotates giving the Earth a magnetic field

Layers of the Earth  Inner Core The inner core is made of solid iron The closest model of the inner core we have is an iron nickel meteorite The inner core is under extreme pressure crust mantle Outer core Inner Core

How do we know about the layers of the Earth?  To date, humans have never drilled through the crust of the Earth.  Scientists study where waves from earthquakes end up around the globe.  The waves move differently through different densities of material.

GEOLOGIC PROCESSES

Spreading center Collision between two continents Ocean trench Plate movement Subduction zone Oceanic crust Continental crust Material cools as it reaches the outer mantle Cold dense material falls back through mantle Hot material rising through the mantle Mantle convection cell Two plates move towards each other. One is subducted back into the mantle on a falling convection current. Mantle Hot outer core Inner core Plate movement Tectonic plate Oceanic tectonic plate Oceanic crust

The Earth’s Major Tectonic Plates EURASIAN PLATE NORTH AMERICAN PLATE ANATOLIAN PLATE JUAN DE FUCA PLATE CHINA SUBPLATE CARIBBEAN PLATE PHILIPPINE PLATE ARABIAN PLATE AFRICAN PLATE PACIFIC PLATE SOUTH AMERICAN PLATE NAZCA PLATE INDIA- AUSTRALIAN PLATE SOMALIAN SUBPLATE ANTARCTIC PLATE Divergent plate boundaries Convergent plate boundaries Transform faults

The Earth’s Major Tectonic Plates

Hawaiian Island Hot Spot

How the hotspot works

History of Continental Drift Hypothesis  1596 Abraham Ortelius: fit of South American & African coasts  1620 Francis Bacon: noted same fit  1782 Benjamin Franklin: suggested that crust of Earth "floated" on fluid interior (crust broken and disordered by movement of fluids)  1885 Edward Suess Similarities between Late Paleozoic plant fossils of Africa, India, South America, Australia & Antarctica Carboniferous glaciers on Africa, S. America, Australia, Inda Southern supercontinent of Gondwana Gondwana named after province in India where there was glacial and plant evidence (Glosopteris flora) Landbridges, which sank beneath the sea, connected present continent

 Continental movement not a new idea  Wegener developed hypothesis of "continental drift”.  Proposed "continental drift" - published "Origin of Continents and Oceans" in 1915 Pangaea ("all land") existed about 200 Ma Showed breakup in series of maps Few supporters - mostly European and African geologists Ridiculed by American geologists Can't "sail" continents through oceans (granitic continents too weak to move through stronger basaltic crust No mechanism to explain movement (Wegener's tidal forces => too weak) Land bridges the answer to explain fossils