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Telling Rocks Apart zHow geologists tell apart different minerals and rocks ycolor, luster, texture yhardness test xscratching one against another diamond is hardest yacid test xusing weak hydrochloric acid to ystreak test xform a streak across a ceramic tile
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HNRS 228 AstrobiologyChap.4 Geology Bennett et al.
Lecture Notes for Chapter 4(mostly from HNRS 227)Prof. Geller
The Geological HistoryReading the Earth’s history in the rocks
Rocks and fossils Relative and absolute dating methods
Formation of the Earth Accretion, differentiation, Moon, age
The Hadean EarthPlate TectonicsClimateGeology and life
Telling Rocks ApartHow geologists tell apart different
minerals and rocks color, luster, texture hardness test
scratching one against another• diamond is hardest
acid testusing weak hydrochloric acid to
streak testform a streak across a ceramic tile
Minerals(see Table 19.1)Characteristics
naturally occurring inorganic definite crystalline structure
The natural resources of industry
Igneous Rocks
“Rocks formed from hot molten mass of melted rock material”
Sedimentary Rocks
“Rocks formed from particles or dissolved materials from previously existing rocks.”
Metamorphic Rocks
“Previously existing rocks that have been changed by heat, pressure, or hot solutions into a distinctly different rock.”
The Rock Cycle
Earth’s Interior andHow We Know It
Earthquakes Galore
Earth’s Inside Story
Crustal Rumblings
Plate Tectonics“The theory that the Earth’s crust is
made of rigid plates that float on the asthenosphere.”
Consider the scientific evidence for plate tectonics and what forced scientists to accept the theory as fact
Fossils across an ocean
Boundaries Galore
Plates are smashing
Surface Building ProcessesStress
“stress is a force that tends to compress, pull apart, or deform”
different types of stresscompressive stresstensional stressshear stress
Strain “the adjustment to stress”
Stress and Strain
Surface Building Processes
Folds bends in
layered bedrockAnticline /\
Syncline \/
Surface Building ProcessesFaulting
formation of a crack caused by relative movement of rock on either side of a fracturedifferent types - normal, reverse, thrust
Earthquakes Defined as
“quaking, shaking, vibrating, or upheaval of the ground”
Earthquake causes elastic rebound
theory Intensity measure
Richter Magnitude not linear
Mountains“elevated parts
of the Earth’s crust that rise abruptly above the surrounding surface”
Causes folding, faulting,
volcanic activity
Volcanoes“hill or mountain formed by the extrusion of lava
or rock fragments from magma below”Different types
shield, cinder cone, composite (composite shown)
Tear-Down ProcessesWeathering
mechanical weathering chemical weathering
Erosion mass movement (mass wasting) running water (floodplain, delta) glacier wind (deflation and abrasion) impact cratering
Development of Geologic TimeFossilization“Reading the Rocks”
principle of uniformity principle of original horizontality principle of superposition principle of crosscutting relationships principle of faunal succession radiometric dating
Geologic Time Scale
Geologic Time Scale