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Download Mountains, Folds, & Faults What happens to the Earth’s crust
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Mountains, Folds, & Faults What happens to the Earth’s crust when forces are applied to it. Objective #1 - Forces (Copy this table.) Direction Name of Force Cause • Tension - a pulling, stretching force. • Caused by the divergent part of convection where magma comes up and then spreads to the sides. or • Caused by elastic rebound. • (1789) • Compression - a squishing force. • Caused by plate collisions. • (1788) • Buoyancy or Isostacy - a lifting force. • Caused by density differences in a fluid. • Gravity - a force pulling downward. • Nobody knows what causes gravity. ( We do know that both mass and distance influence the amount of force - Thanks Newton :) • If you figured out what causes gravity, you would win the Nobel Prize in Physics! Objective #2 Styles of Deformation • How the Earth’s crust responds to stress. Elastic Deformation • When a force is applied the crust becomes deformed. • When the force is released - the crust returns to its original shape (but possibly offset). Plastic Deformation • When a force is applied - the crust becomes deformed. • When the force is released - the crust stays deformed. Brittle Deformation • When a force is applied - the crust breaks! • (1788-9) Objective #3 (Copy this table.) Temperature • High • Plastic • Low • Brittle Duration = how long • Long time • Plastic • Short period • Elastic Moisture Present • Wet • Plastic • Dry • Brittle Amount of Force • A lot • Brittle • A little • Plastic or Elastic Speed Force is Applied • Fast • Brittle • Slow • Elastic or Plastic Age of Crust • Old • Brittle • Young • Elastic or Plastic Depth • Deep • With depth comes heat and moisture. • Plastic • Remember that many geologic features you see at the surface formed way underground. • Shallow • Shallow will be dry and cool. • Elastic or Brittle (Others) • (High) • (Low) (Other Considerations) • The type of material combined with the type of force make a big difference! • Bridges Isostacy • Means standing the same. • Saucer dispenser at café • Crust thickness Objective #4 Structures Anticline = an Upfold • Force = compression • Style = plastic • (17917,1834,1937,1826) Syncline = a Downfold • Force = Compression • Style = Plastic • (1854, 1860, 1862, 1867, 1869, 1938, 1839) Faults Normal Fault • Force = Tension • Style = Brittle • The side on top of the slope (headwall) naturally slides down the slope (footwall). (26938, 1802, 1817, 1908, 1899, 1900, 1925) Reverse Fault • Force = Compression • Style = Brittle • The side on top of the slope (headwall) is pushed up the slope (footwall). • (27119, 1803, 1901, 1903,1816, 1895) • • • • Transform Fault Force = Compression or Tension Style = brittle Two pieces move side-by-side. (27300, 1804, 1911) Dome Mountains • • • • Force = Buoyancy Style = Plastic Rising magma bends overlying rock layers upward. (1798, 1861) Folded Mountains • Force = Compression • Style = Plastic • Compression folds layers into synclines and anticlines. The surface becomes ridges and valleys. (3559) Fault Block Mountains • • • • Force = Tension or Compression Style = Brittle Blocks move up or down along parallel faults. (1812, 3558) Volcanic Mountains • Formed by eruption of lava that piles up to form a mountain. How to prepare for the TEST: • The drawing below shows a piece of the Earth’s crust before force was applied. • Draw an after structure that would result from each of the following cases. • A) Compression with plastic deformation • B) Tension with brittle deformation • C) Compression with brittle deformation TEST preparation cont’d. • If the drawing below shows the upper surface of the Earth’s crust, draw the bottom of the crust. TEST preparation cont’d. • We went over all of your objectives. • Study your notes and practice each objective. • Don’t forget to make flash cards for EXTRA CREDIT!!!
