Geology of Landscapes Chapter 6 (Building Earth s Surface Faulting and Folding)

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1 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 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 _

2 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

3 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. Anticline Syncline Dome Basin Monocline -shaped fold Kinds of Folds 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

4 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?

5 Evolutionary Belief vs Creationist Belief Principle of Uniformity vs. The Great Flood James ( ) 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

6 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

7 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,

8 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

9 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 Hanging wall Fault 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

10 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?