1. Geologic Concepts

2. MAJOR SUBDIVISIONS OF GEOLOGIC TIME:
Geologic Time Scale- A record of Earth’s history, beginning 4.6 billion years ago, that shows events time units, and history.
MAJOR SUBDIVISIONS OF GEOLOGIC TIME:
Eras- based on differences in life-forms. Example: Mesozoic Era is ended by the marked extinction of dinosaurs and many other organisms about 66 million years ago.
Periods- based on the types of life existing at the time and on geologic events
Epochs- subdivisions of periods. Only the Cenozoic Era is subdivided further into epochs.

3. The Earth Is a Dynamic Planet
Geology: study of dynamic processes taking place on earth’s surface and in earth’s interior
Three major concentric zones of the earth
Core (inner-solid metal & outer- molten metal)
Mantle (rocky & upper: asthenosphere-molten)
Crust
Continental crust
Oceanic crust: 71% of crust
Figure 14-3: The earth is composed of a core, mantle, and crust, and within the core and mantle, dynamic forces have major effects on what happens in the crust and on the surface.

4. The Earth Beneath Your Feet Is Moving
The earth’s crust is broken into tectonic plates
“Float” on the asthenosphere
Much geological activity takes place at the plate boundaries
Figure 14-18: The earth’s crust has been fractured into several major tectonic plates. White arrows indicate examples of where plates are colliding, separating, or grinding along against each other in opposite directions.

5. The Earth Beneath Your Feet is Moving
Plate tectonics
Theory explaining the movement of tectonic plates and the processes that occur at their boundaries
More commonly referred to as “continental drift” theory
Plates slide across surface of earth and can break or collide
Plate boundary = area where 2 plates meet

6. The Earth Beneath Your Feet is Moving
Convection currents cause plate tectonics
Move 2-15 cm per year

7. The Three Types of Plate Boundaries: Divergent
Two plates move apart as magma (liquid rock) rises upward to create new lithosphere
“Seafloor spreading”: new curst on ocean’s bottom & subduction of heavier oceanic plates beneath less dense continental plates

8. The Three Types of Plate Boundaries: Divergent
Example: Mid- Atlantic Ridge/Iceland
Giant undersea mountain range
Formed 20 million years ago as Africa & South America separated

9. The Three Types of Plate Boundaries: Convergent
Where plates meet:
Oceanic & continental
Continental & continental
Oceanic & Oceanic
“Subduction zone”-One plate is subducted (sideways and downward under) another
Tends to lead to mountain ranges and volcanoes Ex. Andes Mountains, Marianas Trench in ocean

10. The Three Types of Plate Boundaries: Transform
Where plates slide past each other
Most famous example: The San Andreas Fault in California

11. Volcanoes Release Molten Rock from the Earth’s Interior
Magma rising through the lithosphere reaches the earth’s surface through a crack
Eruption – release of lava, hot ash, and gases into the environment, determines shape of volcano
Form at divergent plate boundaries, subduction zones & over hot spots

12. Types of Volcanoes Cinder cone Shield cone Steep cones Wider bases
From violent eruptions
Shield cone
Wider bases
From quiet eruptions

13. Types of Volcanoes Composite Cones Hotpots From alternating eruptions
Chains of volcanoes that form when mantle pass over a relatively small, long- lasting, hot region
Examples: Hawaiian/ Galapagos Islands

14. The Ring of Fire Lots of volcanoes and earthquakes
Very active plate boundaries

15. Earthquakes Are Geological Rock-and-Roll Events
Breakage and shifting of rocks
At a fault
Seismic waves
Vibrations in the crust
Focus – origin of earthquake
Magnitude – severity of earthquake
Amplitude – size of the seismic waves
Primary effects: shaking
Secondary effects: rockslides, fires, flooding, tsunamis
Figure 14-19: The San Andreas Fault, created by the North American Plate and the Pacific Plate sliding very slowly past each other, runs almost the full length of California (see map). It is responsible for earthquakes of various magnitudes, which have caused rifts on the land surface in some areas (photo).

16. Earthquakes Are Geological Rock-and-Roll Events
Elastic Rebound Theory:
When a fault is locked, stress builds up until rocks fracture
Move & return close to their original locations
Movement creates waves in rocks

17. Seismic Waves P-waves (Primary waves) Fastest
Travel through solid/liquids
Compression waves (push-pull)
S-waves (Secondary waves)
only through solids
Side to side wave (sine wave)
L-waves (Surface waves)
Only on the surface
Up and down

18. Liquefaction of recent sediments causes buildings to sink
Two adjoining plates move laterally along the fault line
Earth movements cause flooding in low-lying areas
Landslides may occur on hilly ground
Figure 14-21: An earthquake (left) is one of nature’s most powerful events. The photo shows damage from a 2010 earthquake in Port-au-Prince, Haiti.
Shock waves
Focus
Epicenter
Fig , p. 367

19. Earthquakes Are Geological Rock-and-Roll Events
Richter scale
Insignificant: <4.0
Minor: 4.0–4.9
Damaging: 5.0–5.9
Destructive: 6.0–6.9
Major: 7.0–7.9
Great: >8.0
Largest recorded: 9.5 in Chile, 1960

20. Earthquakes on the Ocean Floor Can Cause Huge Waves Called Tsunamis
Series of huge waves generated when ocean floor suddenly rises or drops
Travels several hundred miles per hour
Figure 14-22: This diagram illustrates how a tsunami forms. The map shows the area affected by a large tsunami in December 2004—one of the largest ever recorded.

21. Earthquakes on the Ocean Floor Can Cause Huge Waves Called Tsunamis
2011 – Japan tsunami
Damaged nuclear reactors
Detection of tsunamis
Buoys in open ocean
December 2004 – Indian Ocean tsunami
Magnitude 9.15 and 31-meter waves at shore