ESCI_1012_05

ESCI_1012_05 - 1/23/2012 PlateTectonicsII...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
1/23/2012 1 Plate Tectonics II How Fast Are Tectonic Plates Moving? “Core” Based and Space Based method Reading: 26 31, GPS handout Core Based and Space Based methods Ocean floor magnetism GPS Geological Rates Real Time Rates Fig. 2 4, p. 18
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
1/23/2012 2 Plate Margins And How Fast Plates Move The lithosphere currently consists of 12 large plates. e.g., South American Plate, African Plate All are moving at speeds ranging from 1 12 cm/yr year. Earthquake Epicenters Mark Locations of Plate Boundaries Plate Names Earth as a Magnet Geomagnetic Field at surface is similar to a magnetic Field points in dipole North magnetic pole aligned with rotation axis Magnetic Field Reverses Polarity Magnetic minerals in rocks can record polarity of field Field points out Jordan & Grotzinger
Background image of page 2
1/23/2012 3 Discovery of Marine Magnetic Anomalies USGS Marine Magnetic Anomalies hi h Magnetometer instrument that measures slight variations in the Earths’ magnetic field Positive magnetic anomaly high + low - 5 km Negative magnetic anomaly OCEAN CRUST Anomalies have Symmetry with ridge axis
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
1/23/2012 4 Development of the Theory Confirmation of seafloor spreadi ng in mid 1960s Alternating polarity of Earth’s magnetic field is recorded in volcanic rocks of ocean floors Vine and Matthews (early 1960s) found striped alternating magnetic pattern, parallel to mid oceanic ridge Pattern represents rocks formed at ridge in past periods of Earth’s alternating magnetic field polarity Rocks at ridges found to be young (< 1 million years old); rocks at trenches much older Glen, The Road to Jaramillo, 1982 Sea Floor Spreading Larochelle interpreted the pattern (1963 1965) + Geomagnetic Reverals Ridge axis
Background image of page 4
1/23/2012 5 Magnetic Mapping can measure the rate of seafloor spreading Distance away from ridge Age of oceanic crust Velocity of spreading = Distance/time Sea Floor Age Map
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
1/23/2012 6 Hot Spots and Hot Spot Track oldes youngest Another way to estimate the rates of plate motions oldest Rising magma from the deep mantle Possibly from core mantle boundary Fig. 2 17, p. 27
Background image of page 6
1/23/2012 7 Plate Velocities: Geological Rates Based on Magnetism of Oceanic Crust and Radiometric Dating of lava flows Skinner and Porter Roll back the Anomalies back to their ridges and move the Plates Present Day Reassemble PANGAEA
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
1/23/2012 8 0 Ma NAM EUR AFR SAM The reconstructions are from C.R. Scotese’s PALEOMAP Project 20 Ma
Background image of page 8
1/23/2012 9 40 Ma 60 Ma
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
1/23/2012 10 80 Ma 100 Ma
Background image of page 10
11 120 Ma 140 Ma
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 21

ESCI_1012_05 - 1/23/2012 PlateTectonicsII...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online