1. HNRS 227 Lecture #19 Chapter 20 The Earth’s Surface presented by Prof. Geller 31 October 2002

2. Key Points of Chapter 19 zSurface Building Processes zEarthquakes zMountains zVolcanoes zSurface Tearing Down Processes zDetermining Geologic Time zGeologic Time Scale

3. Surface Building Processes zStress y“stress is a force that tends to compress, pull apart, or deform” ydifferent types of stress xcompressive stress xtensional stress xshear stress zStrain y“the adjustment to stress”

4. Stress and Strain

5. Surface Building Processes zFolds ybends in layered bedrock zAnticline/\ zSyncline \/

6. Surface Building Processes zFaulting yformation of a crack caused by relative movement of rock on either side of a fracture xdifferent types - normal, reverse, thrust

7. Earthquakes zDefined as “quaking, shaking, vibrating, or upheaval of the ground” zEarthquake causes yelastic rebound theory zIntensity measure yRichter Magnitude xnot linear

8. Mountains z“elevated parts of the Earth’s crust that rise abruptly above the surrounding surface” zCauses yfolding, faulting, volcanic activity

9. Volcanoes z“hill or mountain formed by the extrusion of lava or rock fragments from magma below” zDifferent types yshield, cinder cone, composite (composite shown)

10. Tear-Down Processes zWeathering ymechanical weathering ychemical weathering zErosion ymass movement (mass wasting) yrunning water (floodplain, delta) yglacier ywind (deflation and abrasion) yimpact cratering

11. Development of Geologic Time zFossilization z“Reading the Rocks” yprinciple of uniformity yprinciple of original horizontality yprinciple of superposition yprinciple of crosscutting relationships yprinciple of faunal succession yradiometric dating zGeologic Time Scale

12. Geologic Time Scale