* Active Continental Margins * Geologically active with plate boundaries leading to earthquakes, young mountain belts, and volcanoes * Ocean trench: narrow, deep trough parallel to the edge of a continent or an island arc * Deepest parts of the ocean * Mid Ocean Ridges and Trenches * Seamounts and Guyots * Seamounts: conical undersea mountains that rise 1000 meters or more above the sea floor * most are extinct volcanoes (except near mid-ocean ridge or hot spot) * chains of seamounts form aseismic ridges (no earthquakes) * Guyots: flat-topped seamounts * Cut by wave action * Reefs common around them * Reefs: wave-resistant ridges of coral, algae, and other calcareous organisms (calcium carbonate anatomical structures) * Fringing reefs: flat, table-like reefs attached directly to shore * Barrier reefs: parallel to the shore but are separated by wide, deep lagoons * Atolls: circular reefs that rim lagoons * Sea Floor Sediments * Terrigenous sediments: land-derived sediments hat have found their way to the sea floor * Comprise continental rise and abyssal plains * Pelagic sediments: settle slowly through the ocean water, and are derived from fine-grained clay (delivered primarily by wind) and skeletons of microscopic * Oceanic Crust * Recall: thinner and different composition than continental crust * Layer 1 – marine sediment of various composition and thickness * Layer 2 – pillow basalt overlying basalt dikes * Layer 3 – sill-like gabbro intrusions * XVIIII: Plate Tectonics 3/27/12 * Plate Tectonics – theory that Earth’s surface is composed of large, thick plates that move and change in size * Alfred Wegener said that continents have identical late Paleozoic rocks and fossils * Certain plant and animal fossils were found on all 5 continents, reptile fossils were found only in Brazil and south Africa * Pangeaea: supercontinent proposed by Wegener * Laurasia – northern supercontinent containing North America and Eurasia (excluding India) * Gondwanaland – southern supercontinent containing South America, Africa, India, Antarctica, and Australia * VIIII: Mass Wasting 3/29/12 * Downhill movement of masses of bedrock, rock debris, or soil, driven by the pull of gravity * Mass wasting is, with proper planning, is perhaps the most easily avoidable of all geologic hazards * Mass movements occur everywhere and cause damages that are costly, but don’t cause many deaths * Earth’s Systems * Atmosphere * Interaction between atmosphere and rocks – chemical weathering * Hydrosphere * Water is a primary contributor to landslides * Biosphere * Vegetation can sometimes act to stabilize soil * In other cases plant roots may contribute to destabilization (e.g., trees on dams) * Classification of Mass Wasting * 1. Rate of movement * 2. Type of material – solid bedrock or soil (unconsolidated material at Earth’s surface) * 3. Type of movement * Flow * Slide * Fall * Forces Associated with Mass Wasting * Gravity – the driving force for mass wasting, includes two components: * 1. Normal force: perpendicular to slope, component that ‘holds’ block in place * 2. Shear force: parallel to the slope, component that ‘pulls’ block down slope * Shear strength: resistance to movement or deformation; controlled by composition of material and water * Forces that control mass movement * Gravity is principle factor * Steepness of slope: steeper slope = larger shear force * Water: pore pressure from water decreases shear strength * Stable vs. Unstable
What observations support the continental drift hypothesis?
the similarities in shape between continents
evidence of climate change
How do observations of earthquake and volcanic activity support the theory of plate tectonics?
there are more volcanos and earthquakes at the edge of tectonic plates
What evidence in support of plate tectonics is provided by studies of the ocean floor?
there is a chain of volcanic mountains on the ocean floor that are laid out to outline parts of a…
University of Phoenix Material
Effects of the Motions of Tectonic Plates Worksheet
From Visualizing Earth Science, by Merali, Z., and Skinner, B. J, 2009, Hoboken, NJ: Wiley. Copyright 2009 by Wiley. Adapted with permission.
This diagram was similar to one Alfred Wegener drew to show the distribution of continents 300 million years ago. His theory of continental drift was met with skepticism in the scientific community.
1. Describe three forms of evidence Wegener…
The Geography of the Ocean Basins
• The oceans (Atlantic, Pacific, Indian, Arctic,
and Southern) are not distributed evenly
– Two-thirds of land found in Northern Hemisphere
– 80% of Southern Hemisphere is ocean
• A number of shallow seas are connected to
the main ocean basins
• All ocean basins are inter-connected, and
together constitute 1 world ocean
One World Ocean
mountains appear randomly. However that isn’t the case- they are caused by plate tectonics. Plate tectonics are a scientific theory that pertains to the large-scale motions of the Earth’s lithosphere (the rigid outermost shell) and formed form extreme core pressure. The concept of plate tectonics developed during the early 20th century and is the study of the mass of the earth and how the masses correlate to one another. The plates pull and push causing continental drift, which affects the earth by causing…
Sea floor Spreading
With the discovery of plate tectonics and the mapping of the earth into about 12 plates, plus the understanding that plates' movement caused earthquakes, Alfred Wegener's idea of "continental drift" looked less ludicrous than his contemporaries had thought. There still seemed to be no way that continents could plow through the earth's surface on their own, but perhaps something else could explain how the land masses had once been joined.
Harry Hess was a geologist and Navy…
-Provides the mechanisms for the next segment of class
- Earth is a dynamic system not only as climate, but in
solids as well
- Rock solids move and interact
- Source of energy is from within the Earth
- Residual heat from Earth’s formation
- Very term and concept heavy. Get these things down…
Components of Earth
Crust (two types)Oceanic Crust- Thin,
dense crust formed
at mid-ocean ridges
correct, but technology had not yet advanced to the point that Wegener could use the scientific method to prove his Continental Drift theory, which states that land mass is moved, via the tectonic plates. There are three types of plate boundaries moving the plates; divergent, convergent and transform. These move the plates in various directions causing the continents to form valleys, mountains, volcanos, islands, hot spots, and earthquakes.
Another way to shape the landscape is through human interference…
10. What is the Richter Scale and what does it measure?
11. What effects do earthquakes have on the Earth?
12. What is a tsunami or seismic sea wave?
13. Is it correct to call these seismic sea waves tidal waves? Why or why not?
14. Name 3 major zones of earthquake activity.
15. What are the 3 types of plate boundaries? Explain each.
16. What is subduction?
INTERIOR OF THE EARTH:
1. What is geophysics?
2. What is seismic reflection?
3. What is seismic…
Plate Tectonics Midterm Project
Purpose: Students will research types and locations of different plate boundaries found on planet Earth and discover how these boundaries have influenced the culture in a particular location.
***Do not plagiarize, all work must original***
***All work must be typed***
Part I (100 pts)
Choose a Plate Boundary from one of the following boundaries
India (Himalayas Mountains)
Andres Mountains (South America)