Earthquakes, Earthquakes, Volcanoes & The Ring Volcanoes & The Ring

of Fireof Fire

1. Convection in Earth’s Mantle—heat from 1. Convection in Earth’s Mantle—heat from Earth’s core and the mantle itself cause Earth’s core and the mantle itself cause convection currentsconvection currents in the mantle. in the mantle.

2.2.Continental Drift: Continental Drift: Wegener’s idea that the Wegener’s idea that the continents slowly moved over Earth’s surface. continents slowly moved over Earth’s surface.

3. 3. Wegener’sWegener’s hypothesis was that all the hypothesis was that all the continents had once been continents had once been joinedjoined together together ((PangaeaPangaea) and has since drifted apart. ) and has since drifted apart.

His hypothesis was originally His hypothesis was originally rejectedrejected by by scientists, and now it is believed he was scientists, and now it is believed he was correct.correct.

Continental Drift Animation

He believed this based He believed this based on 3 types of on 3 types of evidence:evidence:

a. Evidence from a. Evidence from LandformsLandforms

b. Evidence from b. Evidence from FossilsFossils

c. Evidence from c. Evidence from ClimateClimate

4. 4. Mid-Ocean RidgeMid-Ocean Ridge—the longest chain of —the longest chain of mountainsmountains in the world; curves like the in the world; curves like the seam of a baseball along the sea floor, seam of a baseball along the sea floor, extending into allextending into all of Earth’s oceans.of Earth’s oceans.

Q: How did scientists map the mid-ocean Q: How did scientists map the mid-ocean ridge? ridge? sonarsonar

5. At the mid-ocean ridge, 5. At the mid-ocean ridge, molten molten materialmaterial rises from the mantle and rises from the mantle and eruptserupts. The molten material then . The molten material then spreads out, spreads out, pushingpushing older rock to both older rock to both sides of the ridge.sides of the ridge.

6. 6. Sea-floor Spreading: Sea-floor Spreading: the process that the process that continually adds new material to the continually adds new material to the ocean floorocean floor

Sea-Floor Spreading Animation

7. There are 3 types of 7. There are 3 types of evidence of sea-floor evidence of sea-floor spreading:spreading:

a. molten a. molten materialmaterial near near the mid-ocean ridge had the mid-ocean ridge had a strange shape, like a strange shape, like pillows, which can only pillows, which can only form when molten form when molten material coolsmaterial cools

b. magnetic b. magnetic stripesstripes

c. drilling c. drilling samplessamples from from the ocean floor found the ocean floor found that samples of rocks that samples of rocks nearest the mid-ocean nearest the mid-ocean ridge were ridge were youngeryounger than than the samples of rock that the samples of rock that were farther awaywere farther away

8. At deep-ocean trenches, 8. At deep-ocean trenches, subductionsubduction allows part of allows part of the ocean floor to the ocean floor to sinksink back into the mantle. back into the mantle.

9. The Theory of 9. The Theory of Plate Tectonics Plate Tectonics —explains the —explains the formation, movement, and subduction of Earth’s formation, movement, and subduction of Earth’s plates. The plates move only plates. The plates move only oneone to to tenten cm per year. cm per year.

10.10. Plate Boundaries Plate Boundaries (illustrate each of the following)(illustrate each of the following)

a. Transform a. Transform BoundariesBoundaries

b. Divergent b. Divergent BoundariesBoundaries

• c. Convergent c. Convergent BoundariesBoundaries

• d. Collisional d. Collisional BoundariesBoundaries

11. Plate 11. Plate movement can movement can alter Earth alter Earth systems and systems and produce produce changeschanges in Earth’s surface in Earth’s surface such as faulting, such as faulting, earthquakes, earthquakes, volcanoes, rift volcanoes, rift valleys, mountain valleys, mountain building, trenches building, trenches and volcanoes- and volcanoes- just to name a just to name a few!few!

12. Faults usually 12. Faults usually occur along occur along plate plate boundaries.boundaries.

13. 13. EarthquakesEarthquakes- - Movement along Movement along a fault releases a fault releases strainstrain energy. energy. When this When this potential energy potential energy is released, it is released, it moves outward moves outward from the fault in from the fault in the form of the form of seismicseismic waves. waves.

14. The 14. The focusfocus of an earthquake is the of an earthquake is the point inside Earth where it starts. The point inside Earth where it starts. The epicenterepicenter is the point on Earth’s surface is the point on Earth’s surface located directly above the focus. Seismic located directly above the focus. Seismic Waves emanate from this point.Waves emanate from this point.

15. Most earthquakes occur in well-known 15. Most earthquakes occur in well-known belts. About belts. About 80%80% of them occur in the of them occur in the Pacific Pacific RingRing of of FireFire- the same belt in which - the same belt in which many of Earth’s many of Earth’s volcanoesvolcanoes form. form.

Focus, Epicenter Animation

16. When plates 16. When plates collidecollide, rather than being , rather than being subducted, the plates pile into each other, subducted, the plates pile into each other, causing one or both plates to fold up like an causing one or both plates to fold up like an accordion. This process elevates the crust, accordion. This process elevates the crust, folds and deforms it heavily, and produces a folds and deforms it heavily, and produces a mountainmountain range. range.

17. Folding and 17. Folding and faulting that is faulting that is driven by driven by plateplate movementmovement results in results in mountain mountain building.building.

18. 18. Rift ValleysRift Valleys occur along occur along divergent divergent boundaries where boundaries where the plates the plates separate separate or are or are moving away moving away from one another.from one another.

19. 19. Land SubsidenceLand Subsidence occurs when the land occurs when the land surface sinks as a surface sinks as a result of geologic result of geologic processes or human processes or human activities.activities.

20. 20. TrenchesTrenches are are deep, linear, relatively deep, linear, relatively narrow depressions in narrow depressions in the sea floor, formed the sea floor, formed by the subduction of by the subduction of oceanic plates (where oceanic plates (where one plate slides one plate slides beneath the other).beneath the other).

21. Most volcanoes occur along 21. Most volcanoes occur along divergingdiverging plate boundaries; most plate boundaries; most are along the edge of the are along the edge of the continents.continents.

Plate Boundaries

22. 22. VolcanoesVolcanoes form 2 ways: form 2 ways:

a. One way is a. One way is when two oceanic when two oceanic plates collideplates collide. . This can produce This can produce a a stringstring of of volcanic volcanic islandsislands like the Caribbean like the Caribbean Islands.Islands.

b. The second way volcanoes can form is when b. The second way volcanoes can form is when an oceanic plate collides with a continental an oceanic plate collides with a continental plate. The older and denser oceanic plate plate. The older and denser oceanic plate subductssubducts, or sinks below the less dense plate. , or sinks below the less dense plate. Rock in and above the sinking plate melts, Rock in and above the sinking plate melts, forming chambers of forming chambers of magmamagma that erupt. that erupt.