1. Earthquakes and Volcanoes
Landform Geography
Earthquakes and Volcanoes

2. Earthquakes
Sudden release of tectonic stress creates movement in Earth’s crust & shockwaves through lithosphere

3. Earthquake Processes

4. Earthquake Energy Waves released by an earthquake:
P-waves – primary, compressional waves that travel km/sec
S-waves – secondary, vertical waves that travel 60-70% slower than P waves

5. Triangulation to Locate ‘Quake
Known distance to stations A, B and C shows location of epicenter

6. Measuring Earthquakes
Richter Scale – logarithmic measure where each whole number represents 10X the shaking of the next smaller number

7. Faulting
Earthquakes occur along faults – cracks in Earth’s crust where rocks or plates are displaced
Fault Types:
Normal –
Reverse –
Strike-Slip –
Overthrust –

8. Normal Fault

9. Reverse Fault

10. Strike-slip Fault

11. San Andreas Fault
(Transform Fault)
Movement

12. Overthrust fault

13. 1886 Charleston Earthquake

14. 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

15. Where to find volcanoes
Subduction zones, Sea-floor spreading, and Hot spots

16. Cinder-Cone Volcanoes
Small, steep-sided volcano made of magma fragments & rock debris from central vent

17. Composite Volcanoes
Large, steep-sided volcano built up by layers of lava & rock debris – over subduction zones – viscous, silicate magma - explosive eruptions
Mt. Fuji
Cross Section

18. Pacific “Ring of Fire”
Concentration of composite volcanoes around the Pacific Basin over subduction zones

19. Shield and Composite Volcanoes
Mauna Loa, Hawaii

20. Shield Volcanoes
Broad, gentle-sided volcanoes formed from low-silica, low-viscosity magma – lava flows cool & harden to become basalt

21. 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

22. Volcanic Ash

23. 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

24. 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

25. Formation of Hawaii Emperor Seamount Chain Hawaii
70 M yrs old – Pac. Plate
1st moved North, then NW
Hawaii
Kauai Oldest – Big Island
(Hawaii) still over hot spot
70 mya
Present

26. Hot Spot Tracks

27. Calderas from eruptions
Yellowstone Hot Spot
North American Plate has moved west, then northwest over past 16.5 M yrs
Calderas from eruptions
in past 2 M yrs

28. 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

29. Geyser Cross Section

30. Calderas
Large depression formed when a volcanic mountain collapses after erupting
Crater Lake, Oregon