Transcript L03_GeoCycles1

Philosophy and Fundamental Concepts
(unfinished from last lecture)
•Concept 5: Uniformitarianism (James Hutton)
•The present is the key to the past
•Uniformity of Process, not magnitude and frequency
•EG-The present is the key to the future
GLY 2030Cat Siccar Point, Scottish coast
Unconformity
1
Tectonics and Geologic Cycles –
Tectonic, Rock, Hydrologic, Biogeochemical
Part 1: The Tectonic Cycle
Alfred Wegener
German Meteorologist
Gathered Evidence from
Geologic Literature
dared to challenge current
geologic assumptions that
continents were fixed in
place
Fit of Continents / Matching Geologic Units
Locations of Past Glaciations
Locations of Past Equatorial Regions
Distribution of Fossils
Continental Drift Hypothesis
Pangaea = “all land”
“pan-gee-ah”
Alfred Wegener
(1880-1930)
Pacific
Northwest
Tibet
South America
South Atlantic
Japan
Arabian Peninsula
Oceanic
trench
Andes
Interior
Continental
shelf
Conventions in Geology - Shape
Referring to Differences in Topography
Elevation:
height above
sea level
Relief: elevation
difference
Slope:
steepness
1st piece of Evidence:
Earth Shape revealed by sea floor mapping
Oceanic fracture zones
Continental shelves
Submerged
ridges and island
arcs
Plateaus
Linear
island
chains
Continents
Deep ocean
trenches
Mid-ocean ridges
Oceanic plateaus
2nd piece of Evidence:
Locations of Moderate to Strong earthquake locations
(1973-2000)
EQ in belts
Mid-ocean ridges
Southern Eurasia
Trenches
Mountain
belts
Sparse in some regions
3rd Piece of Evidence:
Volcanic Activity around the Pacific Ocean
3rd Piece of Evidence:
Global Distribution of Volcanic Activity
Belts
Mid-ocean ridges (not all shown)
Island arcs next to
trenches
Oceanic
islands
Red Sea and
East Africa
Mountain belts
next to trenches
Sparse in some regions
Compare the distribution of earthquakes (yellow),
volcanoes (orange), and high elevations (brown)
EQ, volcanism,
or mtn. building =
tectonic activity
Belts of tectonic
activity divide
lithosphere into
tectonic plates
Earth’s Magnetic Field
Normal magnetic field
Liquid outer core contains
convection currents
Reversed magnetic field
Magnetometer Data Collection
Magnetometer Data Analysis
Magnetic Data Analysis
Paleomagnetic Record
Magnetic Data Analysis and Comparison
with Rock Record
4th Piece of Evidence:
Magnetic Striping of Sea Floor
Time 1: normal
polarity
Observe how
magnetic reversals
are recorded by a
mid-ocean ridge
Show movie of
seafloor striping
Time 2: reversed
polarity
Build series of
magnetic stripes
over time
4th Piece of Evidence:
Magnetic Striping of Sea Floor
10.02.d
Blackboard Exercise: Calculate Sea floor spreading rate…
5th Piece of Evidence:
Sediment Thickness Pattern
Thickest along passive
continental margins
Thinnest near
mid-ocean ridges
Thick offshore
of large rivers