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