05_Lesson Geo 11 - Geosphere and Philippine Setting.pdf

GEOSPHERE NASA GODDARD SPACE FLIGHT CENTER IMAGE BY RETO STÖCKLI WITH ENHANCEMENTS BY ROBERT SIMMON Regolith Regolith is a region of loose unconsolidated rock and dust that sits atop a layer of bedrock. Regolith is a blanket of unconsolidated, loose, heterogeneous su...

GEOSPHERE NASA GODDARD SPACE FLIGHT CENTER IMAGE BY RETO STÖCKLI WITH ENHANCEMENTS BY ROBERT SIMMON Regolith Regolith is a region of loose unconsolidated rock and dust that sits atop a layer of bedrock. Regolith is a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock. It includes dust, broken rocks, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestrial planets and moons. The term regolith combines two Greek words: rhegos, 'blanket', and lithos, 'rock’. The American geologist George P. Merrill first defined the term in 1897. Plate Tectonics Plate tectonics yields a unified explanation of: Earth’s major surface processes The distribution of earthquakes The distribution of volcanoes The origin of continents and ocean basins The past distributions of plants and animals. The mechanism for deformation and orogenesis. The driving engine of the rock cycle Plates The “plates” in Plate Tectonics are the mosaic fragments of the lithosphere. Tekton means “ to build” The lithosphere, the outermost layer of Earth, is made of... the uppermost mantle, and the overlying crust Crust Continental crust Lighter (less dense) 2.7 g/ cm3 Floats 'higher' on the Earth's surface Usually thicker than oceanic crust (25-70 km) Old Granitic/ felsic Oceanic crust Heavier (more dense) 2.9 g/ cm3 Sinks 'deeper' into the Earth's surface Usually thinner than continental crust (5-10 km) Young Basaltic Earth’s Major Plates Plates may be composed of... only oceanic lithosphere (Pacific plate) only continental lithosphere (Arabian plate) both continental and oceanic lithosphere (North and South American plates) Lithosphere is strong and rigid.  An ocean-continent convergent boundary has an oceanic lithospheric plate subducting beneath continental lithospheric plate. Shallow- to deep-focus earthquakes occur in the subducting oceanic plate and a continental volcanic arc develops in the overriding continental plate.  An ocean-ocean convergent boundary has an oceanic lithospheric plate subducting beneath another oceanic lithospheric plate. Shallow- to deep-focus earthquakes occur in the subducting oceanic plate and an island arc develops in the overriding oceanic plate.  A continent-continent convergent boundary has two colliding continental lithospheric plates. Large tectonic mountain belts can form in this setting, but with no subduction, shallow-focus earthquakes dominate and little if any volcanism occurs. Sutures and suture zones are defined as the sites in orogenic belts wherein ancient oceanic lithosphere was subducted into the mantle Benioff Zone A Wadati–Benioff zone is a planar zone of seismicity corresponding with the down-going slab in a subduction zone. Aka Benioff–Wadati zone or Benioff zone or Benioff seismic zone. Named for the two seismologists, Hugo Benioff of the California Institute of Technology and Kiyoo Wadati of the Japan Meteorological Agency, who independently discovered the zones. Differential motion along the zone produces numerous earthquakes. Wadati–Benioff zone earthquakes develop beneath volcanic island arcs and continental margins above active subduction zones.  An oceanic divergent boundary (or spreading center) has two oceanic lithospheric plate moving away from each other in opposite directions.  A mid-ocean ridge mountain belt forms due to thermal uplift, and much basaltic volcanism occurs along the ridge axis. With no subduction, shallow-focus earthquakes dominate. Mid-ocean ridges are commonly offset by oceanic transform faults.  A continental divergent boundary (or continental rift) forms as continental lithosphere extends and thins. With no subduction, shallow-focus earthquakes dominate.  Continental transform tectonic plate boundaries. These plate boundaries have two continental lithospheric plate moving past each other in opposite directions. With no subduction, shallow-focus earthquakes dominate and little or no volcanism occurs.  Intraplate "hot spots" Hot Spots This is not a tectonic plate boundary, instead, it is a volcanic feature that forms within a plate (either oceanic or continental). Hawaii (oceanic), Yellowstone (continental). The hot spot is the point on the surface of the moving lithospheric plate that is overriding a stationary mantle plume. Volcanic chains are formed as the plate carries older volcanoes away from the hot spot. Oceanic hot spots typically build large shield-type volcanic island chains (e.g., the Hawaiian Islands) that eventually become seamounts as they sink beneath sea level (e.g., the Emperor Seamount chain). Earth's Large-Scale Features Major Continents 1. North America 2. South America 3. Africa 4. Australia 5. Asia 6. Europe 7. Antarctica Features in the continents Mountains: elevated feature of continent Mountain ranges: chains of mountains (e.g., Sierra Madre Range, Cordillera range) Mountain belts: mountain ranges that run across a vast area (usually crosses continents) Features in the continents Cratons – oldest and most stable part of the continental crust (Evers & Editing, 2015) - Platform: Cratons where the basement rock is covered beneath by thick sediments (pink in next figure) - Shield: Cratons where the basement rock is exposed in the surface (orange in next figure)  Platforms, shields and the basement rocks together constitute cratons (kratos = strength). Platform is a continental area covered by relatively flat or gently tilted, mainly sedimentary strata, which overlie a basement of consolidated igneous or metamorphic rocks of an earlier deformation. A shield is a large area of exposed Precambrian crystalline igneous and high-grade metamorphic rocks that form tectonically stable areas. Orogeny Orogeny is a mountain-building process that takes place at a convergent plate margin when plate motion compresses the margin. An orogenic belt or orogen develops as the compressed plate crumples and is uplifted to form one or more mountain ranges. Earth's Large-Scale Features Major Ocean Basins 1. Pacific Ocean - Largest and deepest ocean 2. Atlantic Ocean - Second largest and about half the size of the Pacific Ocean 3. Indian Ocean - Mainly in the southern hemisphere and surrounded by the African, Asian and Australian continents 4. Southern (Antarctic) Ocean - Connects Pacific, Atlantic and Indian ocean at about 50° S latitude 5. Arctic Ocean - Smallest, shallowest, mostly ice-covered ocean http://oceanography.asu.edu/Oc_Sept19_pos.pdf END