Chapter 12 Outline

Chapter 12 Outline - Chapter 12: Tectonics, Earthquakes,...

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Chapter 12: Tectonics, Earthquakes, and Volcanism Introduction Earth’s endogenic sys’s produce flows of heat/material toward surface to form crust; conts processes also make cont’l landscapes, oceanic sea-floor crust, sometimes dramatically; earth sys science providing analysis, warnings to pops in danger of volcanic activity, etc. Tectonic activity has deformed, recycled, reshaped Earth’s crust; most/main tectonic, volcanic zones lie along plate boundaries/hot spots Earth’s Surface Relief Features Relief - vertical elevation diffs in landscape; undulating form of Earth’s surface- topography - has stimulated human invention, adaptation- played vital role in human history Crustal Orders of Relief Our understanding of Earth relief/topog enhanced by modern technology; elevation data put in digital form- digital elevation models ( DEMs ) aid in scientific analysis of topography, area-alt distributions, slopes, etc; landscape’s topog grouped into 3 orders of relief First Order of Relief Coarsest lvl of landforms, consisting of continents, oceans; continental landmasses - parts of curst tht are above/near sea lvl; ocean basins - entirely below sea lvl; ~71% Eart covered by water Second Order of Relief Intermediate lvl of landforms for cont’l (mtn masses- eg Alps, Rockies-, plains, lowlands) & ocean- basin features (cont’l rises, mid-ocean ridges, sub. canyons, oceanic trenches- subduction zones) Third Order of Relief Most detailed; incl indv mtns, cliffs, valleys, hills, other landforms of smlr scale- local landscapes Hypsometry Hypsographic curve-s hows distribution of Earth’s surface by area/elevation in relation to sea lvl; relative to Earth’s 12,756 km diameter, surface= low relief- ~20 km; avg elevation of Earth’s solid surface -2070 m below mean sea lvl; avg elevation for exposed land only +875 m Avg elevation of ocean depths -3800 m; thus oceans, on avg, much deeper than cont’l regs are high Earth’s Topographic Regions 3 orders of relief further generalized into 6 topog. regs : plains, high tablelands, hills, low tablelands, mtns, widely spaced mountains, depressions; 4 continents have extensive plains - areas w/local relief of < 100 m, slope angles of ≤5°; high tablelands (Greenland, Antarctica)- 1520+ ft elevations Hills & low tablelands - Africa; mountain ranges- local relief over 600 m- on each continent; Earth relief, topog constantly changing w/crust-forming processes Crustal Formation Processes Due to tectonic activity, weathering, erosion; former ~slow, cause uplift, new landforms w/mtn building along plate boundaries; 3 categories: 1) Residual mtns/stable cont’l cratons, due to inactive remnants of ancient tectonic activity; 2) Tectonic mtns/landforms, due to active folding, faulting… Crustal movements; 3) volcanic features, frmed by surface accumulation of molten rock fr eruptions Continental Shields All continents have nucleus of ancient crystalline rock-
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Chapter 12 Outline - Chapter 12: Tectonics, Earthquakes,...

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