ch. 2 earth materials & processes. earth materials & processes focus: geologic materials and...
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Ch. 2 Earth Materials & Processes
Earth Materials & ProcessesFocus: Geologic materials and processes most important to the study of the
environment
Objectives:
– Acquire a basic understanding of the geologic cycle and its subcycles (tectonic, rock, hydrologic, biogeochemical)
– Review of some of the important mineral and rock types and their environmental significance
– Appreciation/significance of geologic structures
– Appreciation of the landforms, deposits, and environmental problems resulting from wind and glacial processes
Earth Materials & Processes
1. Geologic cycles & processes (espec. Tectonics)
2. Rocks & Rock Materials
– General properties
– Types/classification (general)
– Geologic structures
3. Surficial Processes: Ice & Wind
Earth (Geologic) Processes
Combinations of Internal and Surficial Processes affect and shape the environment:– Mountain Building Processes (Internal processes)
• Volcanism • Faulting• Folding
– Erosional/Depositional Processes (Surficial: driven by solar energy):• Water/Rivers • Glaciers• Wind• Landslides
Geologic (Earth) Cycles
• Tectonic (plate tectonics)
• Rock Cycle
• Hydrologic Cycle
• Biogeochemical Cycles– Carbon, Nitrogen,
Phosphorous, etc.
Tectonic Cycle
• Tectonic = Large-scale internally driven dynamic earth processes
• Shape and deform the earth’s crust (landforms)
– Mountain building– Continents– Basins
The earth is a differentiated planet with dynamic internally-driven processes
Essentially all parts are in motion, producing:“Plate” motions in the lithosphere: Plate Tectonics
Continuous cycling of “lithospheric” material through:• Formation of new “oceanic” crust at “spreading centers”
• Destruction of older “oceanic” crust at “subduction” zones
• “Islands” of thick, relatively stable, “continental” crust
• These “zones” define plate boundaries
Surface/Crustal Manifestation of Plate Tectonics
Observations/Correlations:
• Types and spatial distribution of plate boundaries
• Correlation between plate boundaries and volcanoes (+ earthquakes)
Two Types of Crust/Lithosphere:
• Oceanic Crust (O)
• Continental Crust (C)
= 2.8 = 2.9
= 4.5
Core = 10.7
Two Types of Crust/Lithosphere:• Oceanic (O):
• forms 70% of earth’s crust• constitutes sea-floor bedrock; ~30 km thick• made of primary volcanic “basalt”; density=2.7-3.0 • Young; No old oceanic crust
• Continental (C):• Thicker (~100 km)• Composition: Less dense sediment/granite• “floats” on denser mantle material• Older
• Mantle– Primary material (from which basalts are derived)– Underlies crust
Plate Boundaries
Most major tectonic activity (volcanoes, earthquakes, etc.), and major topographic features occur (or were formed) at plate boundaries
Main Types of Plate Boundaries
• Divergent (splitting apart)• Convergent (colliding)
• Third Type = Transform (e.g., lateral offset)
Types Plate Motion, Plate Boundaries, and Examples of Associated Landforms/Features
• Divergent (separating):O-O sea-floor spreading/mid-ocean ridges
C-C Continental “rifts”: Red Sea, Rio Grande & Mississippi river valleys, E. African (Kenyan) Rift Valley
• Convergent (colliding):O-O Island arc Subduction; Japan, Aleutians
O-C Continental margin Subduction; Cascades, Andes
C-C Continental collision; Himalayas, Alps, Appalachians
Others: Obduction; Accreted terrain
Divergent Plate Boundaries (splitting)Oceanic Rifts/Ridges
Continental Rifts:– Red Sea; E. Africa– Flood lavas (basalts)
Convergent Plate Boundaries (Colliding)
Continent-ContintentConvergence
• Himalayas
• Alps
• Urals
• Appalacians
Other Types of Convergence & Convergent Features
Oman
Obduction•Coast Ranges•Klammath Mtns.•Oman•Newfoundland
Accreted Terrain:•Olympic Mtns.•Etc.
Lateral offset of divergent boundaries
– Offsets of mid-ocean ridges – San Andreas fault
Transform BoundariesTransform Boundaries
Other Important Types/Features
• Hot Spots:– Hawaiian Islands– Yellowstone, Snake River Plain, Columbia River
Plateau
• Flood Basalt Provinces (within continents)– Columbia River Basalts– India, S. Africa, Greenland, Brazil, Germany, etc.
Hawaiian Hot Spot
Also correlated with distribution of volcanoes and earthquakes (see book)
Plate Tectonics of the Western US
Major tectonic activity (volcanoes, earthquakes, etc.), and geographical features occur at plate boundaries and/or hot spots.
Hydrologic Cycle
Carbon Cycle
Rock Cycle
• Stay Tuned
Summary
• Earth is differentiated and dynamic
• Manifestation of dynamic earth processes in lithosphere = plate tectonics
• Two types of crust: oceanic & continental
• Centers/Zones where crust is formed (spreading) or destroyed (subducted) or accreted define plate boundaries
• Two types of plate boundaries:
– Divergent (splitting/spreading)
– Convergent
Summary con’t• Major “tectonic”/topographic features/events are
localized at plate boundaries (volcanoes, earthquakes, mountains, trenches, hydrothermal vents)
• Other related features:
– Transform boundaries (faults)
– Hot Spots (oceanic & continental)
• Hydrologic Cycle: Water transport & storage system
• Biogeochemical Cycles: Counterpart for chemicals ± biologic systems/storage