July 9, 2013
description
Transcript of July 9, 2013
![Page 1: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/1.jpg)
Landform Geography
Earthquakes and VolcanoesJuly 9, 2013
![Page 2: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/2.jpg)
Earthquakes
• Sudden release of tectonic stress creates movement in Earth’s crust & shockwaves through lithosphere
![Page 3: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/3.jpg)
Earthquake Processes
![Page 4: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/4.jpg)
Earthquake Energy• Waves released by an earthquake:
– P-waves – primary, compressional waves that travel 1.5-8 km/sec
– S-waves – secondary, vertical waves that travel 60-70% slower than P waves
![Page 5: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/5.jpg)
Triangulation to Locate ‘QuakeKnown distance to stations A, B and C shows location of epicenter
![Page 6: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/6.jpg)
Measuring Earthquakes• Richter Scale – logarithmic measure where
each whole number represents 10X the shaking of the next smaller number
![Page 7: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/7.jpg)
Faulting• Earthquakes occur along faults – cracks in
Earth’s crust where rocks or plates are displaced
• Fault Types:– Normal –
– Reverse –
– Strike-Slip –
– Overthrust –
![Page 8: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/8.jpg)
Normal Fault
![Page 9: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/9.jpg)
Reverse Fault
![Page 10: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/10.jpg)
Strike-slip Fault
![Page 11: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/11.jpg)
San Andreas Fault(Transform Fault)
Movement
Movement
![Page 12: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/12.jpg)
Overthrust fault
![Page 13: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/13.jpg)
1886 Charleston Earthquake
![Page 14: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/14.jpg)
Volcanoes
• Mts or hills w/ a conduit down into upper mantle through which magma, ash & gases are ejected
• 3 basic types:– Cinder-cone Volcanoes– Composite (strato) Volcanoes– Shield Volcanoes
![Page 15: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/15.jpg)
• Where to find volcanoes– Subduction zones, Sea-floor spreading, and Hot spots
![Page 16: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/16.jpg)
Cinder-Cone Volcanoes• Small, steep-sided
volcano made of magma fragments & rock debris from central vent
![Page 17: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/17.jpg)
Composite Volcanoes• Large, steep-sided volcano built up by layers of lava &
rock debris – over subduction zones – viscous, silicate magma - explosive eruptions
Cross Section Mt. Fuji
![Page 18: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/18.jpg)
Pacific “Ring of Fire”• Concentration of composite volcanoes around the
Pacific Basin over subduction zones
![Page 19: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/19.jpg)
Shield and Composite Volcanoes
Mauna Loa, Hawaii
![Page 20: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/20.jpg)
Shield Volcanoes• Broad, gentle-sided volcanoes formed from low-
silica, low-viscosity magma – lava flows cool & harden to become basalt
![Page 21: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/21.jpg)
Volcanic Output
• Volcanic ash consists of powder-size to sand-size particles of igneous rock material that have been blown into the air by an erupting volcano.
• An ash field is a geographic area where the ground has been blanketed by the fallout of an ash plume.
• Silicosis
• Dry ash weighs about ten times the density of fresh snow
![Page 22: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/22.jpg)
Volcanic Ash
![Page 23: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/23.jpg)
Volcanic Lightning
• Volcanoes produce 2 kinds of lightning:– First occurs in the smoke– The second is produced by the mouth of the
volcano
• Not all volcanoes produce lightning
![Page 24: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/24.jpg)
Hot Spots• Stationary points in asthenosphere from which a
magma plume intermittently pushes through the crust above
• Plates move over hot spots, carrying deposits of basalt with them
• Hawaii (& the Emperor Seamount Chain) & Yellowstone have been shaped by hotspots
![Page 25: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/25.jpg)
Formation of HawaiiEmperor Seamount Chain70 M yrs old – Pac. Plate
1st moved North, then NW
HawaiiKauai Oldest – Big Island (Hawaii) still over hot spot
70 mya
Present
![Page 26: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/26.jpg)
Hot Spot Tracks
![Page 27: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/27.jpg)
Yellowstone Hot SpotNorth American Plate has moved west, then northwest over past
16.5 M yrs
Calderas from eruptionsin past 2 M yrs
![Page 28: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/28.jpg)
Supervolcano• A supervolcano is an eruption that rates a magnitude
of 8 on the Volcanic Explosivity Index. • The VEI is a scale that rates eruptions on their ejected
volume, plume height and duration. The scale ranges from 0 through 8.
• Only a few dozen eruptions in all of Earth's history are known to have a VEI of 8.
• Two of those eruptions, the Lava Creek eruption (640,000 years ago) and the Huckleberry Ridge eruption (2.2 million years ago), occurred at Yellowstone.
• These eruptions were given the VEI rating because their ejected volume exceeded 1000 cubic kilometers
![Page 29: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/29.jpg)
Geyser Cross Section
![Page 30: July 9, 2013](https://reader036.fdocuments.net/reader036/viewer/2022062321/56813b95550346895da4c871/html5/thumbnails/30.jpg)
Calderas• Large depression formed when a volcanic
mountain collapses after erupting
Crater Lake, Oregon