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Geology of Landscapes Geology of Landscapes Chapter 6 (Building Earth’s Surface – Faulting and Folding) ___________ • Process of _________ that _______ the earth’s ________ Stress and Strain • Any solid material responds to a force in a way that depends on: – pressure (force per unit area) – nature of the material – other factors • temperature ______ to _______ • 1. ________ • 2. _______ deformation (recovery) • 3. ________ deformation (no recovery) • 4. _______ ________ • A _____ that tends to ________, pull apart, or _______ a rock – _______ stress • pushing together or against – __________ stress • pulling apart – ________ stress • sliding past ________ • The adjustment (______) to stress – ________ strain • rocks ________ original shape after stress stops – _________ strain • rocks molded or bent do ______ recover – ______ strain • rock cracks or _________ Rock Response to Stress • 1. Nature of the rock • 2. Temperature • 3. Pressure • 4. Speed of stress Rock Response to Stress • __________ – _____ rocks – located on ______ – stress applied ________ – B represents cooler rocks near surface Rock Response to Stress • _______ Deformation • _______ rocks – ______ _____buried – stress applied gradually – A represents deeply buried, warm rocks, under high pressure Nature of Rock • Quartz and garnet are brittle – _________ and __________ fracture • Mica and calcite are ductile – _________, schist, limestone and _________ fold Folding • _________ – ________ in layered bedrock Parts of a fold • __________ – two sides of a fold • ______ _______ – the imaginary line where two limbs come together • _______ ________ – an imaginary plane which intersects the crest or trough in such a manner that the limbs or sides of the fold are symmetrically arranged with reference to it. Kinds of Folds • Anticline • Syncline • Dome • Basin • Monocline ___________ • ______-shaped fold Syncline • __________ __________ fold – limbs dip inward in opposite directions toward fold axis ________ • _________ bulging fold – __________ or elliptical _____________ – Little Sundance Mountain, WY – Inward facing cliffs ________ • ________ bulging fold – ___________ or elliptical shaped ________ – outward facing cliffs _____________ • No change in dip direction across the fold axis – layers _______ in the ________ direction Monocline, Anticline, Syncline Geosyncline • A very large syncline – E.g., San Joaquin Valley ________ Folds • Anticlines and synclines whose ________ _______ is not ___________ Plunging Folds • Appalachian Ridges and Valleys • Pennsylvania Shapes of Folds (recognize picture) • open folds – weak compression – parallel but opposite forces Shapes of Folds (recognize picture) • Isoclinal Fold – Intense compression – parallel, but opposite forces Shapes of Folds (recognize picture) • Overturned fold – Not parallel, but opposite forces – Upper arch overrides lower trough • Recumbent fold (recognize picture) – beds between arch and trough horizontal Folds Folds in Metamorphic Rock Anticline or Syncline? Anticline or Syncline? Anticline or Syncline? Anticline or Syncline? Type of Fold? Type of Fold? Evolutionary Belief vs Creationist Belief Principle of Uniformity vs. The Great Flood James ______ • (1726-1797) • __________ of __________ Geology • Scottish Farmer • Principle of ________ – major tenet of geology Principle of Uniformity • The evolutionary belief _________ _________ are caused by ______ _______ over a long time period, many of which are operating at the present time. – “The present is the key to the past” The Story of James Hutton • Belief in East/West Europe and North America was that God created the world in about 4000 B.C. • James Hutton assumed his observations at Siccar Point meant that the Earth was unimaginably old (KNOW) – ‘no vestige of a beginning, no prospect of an end’ Siccar Point Uniformists on Rock Formation • Hutton based idea of old earth on assumption – Radiometric dating was developed about 100 years later • He assumed that the same slow processes eroding the Scottish highlands in the present formed the ancient rocks by the North Sea in the past. Sedimentary Rock Formation • Uniformists teach that it takes millions of years for sedimentary rock to form. •Creationists believe that it can take very little time for sedimentary rock to form Rapid Rock formation • Car keys encased in solid sandstone found on Oregon coast – Thought to belong to a 1960’s model car Rapid rock formation • Australian scientists have developed a revolutionary new chemical process that transforms loose sediment into rock within days. – Mimics natural processes. • Does not use strange, synthetic materials Creationists on Rock Formation • Rocks do not take millions of years to form • Rocks only need the right conditions – Floodwaters flowing over the Earth during The Flood dumped the huge deposits of sediment. And the same floodwaters contained the dissolved chemicals that quickly cemented the sediment into rock Folded Rock • Uniformists believe that folded rocks were deformed over millions of years by gradual application of heat and pressure. – assume there was no global flood • Creationists believe that the folding of rocks took place during the Great Flood some 4400 years ago. Creationists on Folding • Rock must have been deformed while the sediment was still unconsolidated and saturated with water. – severely deformed rock with hardly any fracturing • If the rocks had been hard and solid before they were deformed, they would have fractured, not folded. Creationists on Folding • Minerals and texture of the rock indicates no evidence that the rocks had been subjected to much heat or pressure. – bending had taken place at normal temperatures. – Genesis Flood • Involved rapid movement of plates comprising earth’s crust. – the fountains of the great deep broke forth and the floodgates of the heavens were opened’ (Genesis 7:11) • Explains why so much sediment was still soft when it was deformed. – No sooner would floodwaters have deposited great volumes of mud and sand than moving plates would have crumpled and deformed the sediment while it was still saturated. • The Flood also explains the colossal forces needed to fold enormous areas of hard rock. Creationists on Folding • Just as swirls in a rainbow cake were formed quickly before the mix was baked into cake, folds in much of the crust of the Earth were formed quickly in a great watery catastrophe before the rocks were solidified ________ • __________ of rocks in response to stress – Joints – Faults _______ • A _______ in a rock along which ____ appreciable _______ has occurred. Columnar Jointing • The Devil’s Tower, Wyoming ________ • A ______ in the earth’s _______ along which _________ has occurred Fault Plane • The surface along which a rock body has broken and been displaced Types of faults • _______________ of _________ ____________ – angle between plane and imaginary horizontal plane • _____________ of ____________ – dip - up and down – strike - horizontally or sideways – oblique - elements of both directions of movement Hanging Wall and Footwall Classification of Faults • _____________ Faults – ___________ movement • one side moves up and the other side moves down. – __________ and ___________ ______ Fault • Hanging wall _______ • Footwall _____ • _______ Stress • Occurs at _________ plate boundaries Fault Blocks • ___________ Faults • __________ – Dropped-down block • __________ – Upraised block _______ Fault • Hanging wall _____ • Footwall _______ • __________ Stress • Occurs at ___________ plate boundaries __________ Fault • A reverse fault with _________ fault plane • ____________ – hanging wall block completely ___________ footwall • sometimes for miles Strike Slip Fault • ___________ movement along cracked rock – example: ________ __________ Fault • forms due to __________ stress Strike - Slip Fault Oblique Fault • A fault exhibiting __________ a _______ ___________and a __________ __________ Oblique fault • Oblique fault produced during 7.7 magnitude earthquake of 1915 • Pleasant Valley, Nevada What kind of Fault? What kind of Fault? .
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