* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Rocks - Images
Survey
Document related concepts
Age of the Earth wikipedia , lookup
Evolutionary history of life wikipedia , lookup
History of geomagnetism wikipedia , lookup
Paleontology wikipedia , lookup
Provenance (geology) wikipedia , lookup
Geomagnetic reversal wikipedia , lookup
Abyssal plain wikipedia , lookup
Oceanic trench wikipedia , lookup
Composition of Mars wikipedia , lookup
History of geology wikipedia , lookup
Geochemistry wikipedia , lookup
Geology of Great Britain wikipedia , lookup
Algoman orogeny wikipedia , lookup
Transcript
Rocks Chapter 6 3 Types of Rock • Igneous – forms when magma cools • http://geology.com/rocks/igneous-rocks.shtml • Sedimentary – forms when other rocks are eroded and the sediments are deposited and cemented together • http://geology.com/rocks/metamorphicrocks.shtml • Metamorphic - forms when rock undergoes intense heat and pressure • http://geology.com/rocks/metamorphicrocks.shtml Rock Cycle • The types of rock can be changed into any other type • Igneous – Can become sedimentary if it goes through EROSION, DEPOSITION, AND CEMENTATION – Can become metamorphic if it goes through INTENSE HEAT AND PRESSURE Rock Cycle • Sedimentary – Can become igneous if it MELTS AND COOLS – Can become metamorphic if it goes through INTENSE HEAT AND PRESSURE • Metamorphic – Can become igneous if it MELTS AND COOLS – Can become sedimentary if it goes through EROSION, DEPOSITION, AND CEMENTATION Bowen’s Reaction Series Continental Drift Section 10.1 Alfred Wegener • 1912 • Hypothesis of continental drift said that landmass was once a supercontinent, Pangaea • Began breaking up 250 mya • May be reason for mountain ranges Evidence for Continental Drift • Similarities in coastlines • Fossils – Ex: mesosaurus found in South America and western Africa • Rock formations – Ages and types of rocks in western Africa and eastern S. America – Continuing mountain chains Evidence for Continental Drift • Climatic evidence – Glacial debris found in southern Africa and South America – Coal found in Siberia Why the Hypothesis was Opposed • Lacked a mechanism • Died in 1930 before he could find it Redeeming Evidence • Mid-Ocean Ridges – 1947, mapping of Mid-Atlantic Ridge – Found that sediment nearest the ridge is thinner so sediment settled on outer regions for a longer time – Fossils closer to the ridge are younger – Oceanic rocks only 175 myo while continental rocks are 3.8 byo Sea-Floor Spreading • 1950s, Harry Hess – Valley that center of ridge is a rift in Earth’s crust and magma rises to fill the crack – Process named by Robert Dietz – Since ocean floor moving, continents must be moving, too – This could be the missing mechanism for continental drift Even More Evidence • Paleomagnetism – As magma cools, iron-rich sediment aligns with magnetic field of Earth – It has been found that the magnetic field of the Earth has changed through time – Pattern of alternating normal and reversed polarity in rocks – Striped magnetic pattern was mirror image on both sides of rift Wegener Redeemed • Magnetic reversals in rocks found on continental rocks, too. • Now, evidence was present and so was the mechanism. The Theory of Plate Tectonics Chapter 10.2 Plate Tectonics • Theory that explains why and how continents move • Study of formation of features on Earth’s crust How Continents Move • Lithosphere broken into tectonic plates that ride on the asthenosphere • Oceanic crust – dense, rich in Fe and Mg • Continental crust – low density, rich in silica Tectonic Plates • 15 major plates • Knowledge from studying earthquakes • Location of volcanoes Types of Boundaries May be in the middle of ocean floor, edges of continents, or within continents 3 major types: divergent, convergent, transform fault Divergent Boundaries • 2 plates move away from each other • Magma rises to surface, cools, and forms new oceanic lithosphere • Forms mid-ocean ridges and rift valleys Convergent Boundaries • 2 plates collide • 3 types: – Oceanic-continental where oceanic subducts • Deep ocean trenches and volcanic mountains Convergent Boundaries – Continent-continent where neither plate subducts • Forms large mountain ranges Convergent Boundaries • Oceanic-oceanic where one plate subducts under the other – Forms deep-ocean trenches and island arcs (chain of volcanic islands) Transform Fault Boundaries • 2 plates slide past each other horizontally • Do not produce magma • Fracture zones at mid-ocean ridges are transform fault zones Causes of Plate Motion • Convection Causes of Plate Motion • Ridge Push Causes of Plate Motion • Slab Pull – As lithosphere pulls from the mid-ocean ridge, it cools and sinks – The leading edge pulls the rest of the plate