What direction is the Pacific Plate currently moving, based on the chain of Hawaiian Islands with only the easternmost island active? It is not moving; the chain of islands is not related to the active one. Before people understood plate tectonics, what evidence led some scientists to believe in continental drift? Rocks on the ocean floor are oldest in the center, becoming progressively younger toward each continent.
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Earth Structure A. Core, mantle and crust B. Lithosphere C. Asthenosphere D. Isostacy II. Plate Movement A. Lithospheric plates B. Plate tectonics C. Divergent Boundaries 1. Mid-Ocean Ridges D. Convergent Boundaries 1. Subduction Zones 2. Collision Zones E. Transform Boundaries F. Seafloor spreading III. Hazards and Plate Boundaries A. Spreading Centers 2. Rift Zones B. Collision Zones C. Collision of Continents 1. Collision Zone D. Transform Boundaries E. Hotspot Volcanoes 1. Oceanic Hotspots 2.
Development of a Theory A. Pangaea B. Continental Drift 1. Mountain Ranges 2. Age of Rocks 3. Fossils 4. Glaciation C. Seafloor Spreading 1. Magnetic Field 3. Age of Seafloor D. Plate Tectonics E. Scientific Method F. Hypothesis G. Theory KEY TERMS asthenosphere collision zone continental drift convergent boundary core crust divergent boundary hotspot volcano hypothesis isostacy lithosphere lithospheric plate magnetic field mantle mid-oceanic ridge Pangaea plate tectonics rift zone scientific method seafloor spreading spreading center subduction zone theory transform boundary trench KEY POINTS 1.
Earth Structure and Plates Earth is made up of an inner and outer core, surround by a brick mantle and covered by a much thinner crust. The crust and stiff outer part of the underlying mantle is called the lithosphere. The inner, hotter region is the asthenosphere. The concept of isostacy explains why the lower-density continental rocks stand higher than the ocean-floor rocks and sink deeper into the underlying mantle. This behavior is analogous to ice lower density floating higher in water higher density.
A dozen or so nearly rigid lithospheric plates make up the outer 60 to km of Earth. They slowly slide past, collide with, or spread apart from each other. Hazards and Plate Boundaries Much of the tectonic action, in the form of earthquakes and volcanic eruptions, occurs near the boundaries between the lithospheric plates.
Where plates diverge from each other, new lithosphere forms. If the plates are continental material, a continental rift zone forms. As this process continues, a new ocean basin can develop, and the spreading continues from a mid-oceanic ridge, where basaltic magma pushes to the surface. These eruptions form volcanoes on the overriding plates. Continent—continent collision zones, where two continental plates collide, are regions with major earthquakes and the tallest mountain ranges on Earth.
Transform faults involve two lithospheric plates sliding laterally past one another. Where these faults cross continents, such as along the San Andreas Fault though California, they cause major earthquakes. Hotspots form chains of volcanoes within individual plates rather than near plate boundaries. Development of a Theory The hypothesis of continental drift was supported by matching shapes of the continental margins on both sides of the Atlantic Ocean, as well as the rock types, deformation styles, fossil life forms, and glacial patterns.
Continental drift evolved into the modern theory of plate tectonics based on new scientific data, including the existence of a large ridge running the length of many deep oceans, matching alternating magnetic stripes in rock on opposite sides of the oceanic spreading ridges, and age dates from oceanic rocks that confirmed a progressive sequence from very young rocks near the rifts to older oceanic rocks toward the continents.
The scientific method involves developing tentative hypotheses that are tested by new observations and experiments, which can lead to confirmation or rejection. When hypotheses are confirmed by multiple sources of data over a long time, they become a theory—or widely accepted scientific fact.
Discuss the various types of plate boundaries and how they yield natural disasters. It is important that students have a thorough understanding of the types of boundaries and the location in which they occur.
By knowing the type of boundary, scientists can determine the type of disasters that is likely to occur, and where. Have students cite popular examples of certain plate boundaries i. Discuss the structure of the Earth lithosphere plates, asthenosphere, mantle, etc. Explain the scientific method and how it is used by people on a daily basis—not just in a scientific, academic, or research environment.
Tanya Atwater, Univ. Video: Plate Tectonics and Continental Drift. Gould Media, Inc. Box , Santa Barbara, CA. Video: Earth Revealed 6: Plate Dynamics. Geological Survey, 77 p. What does oceanic lithosphere consist of and how thick is it? ANSWER: The top 7 km is low-silica crust; it contains iron- and magnesium-rich minerals basalt over peridotite and is about 60 km thick.
What are the main types of lithospheric plate boundaries, described in terms of relative motions? Provide a real example of each by name or location. Convergent Boundary: Plates collide, old crust is destroyed. Examples include ocean-continent collision, such as the Cascade Ranges and the Andes in South America; ocean-ocean collision, such as the Japanese Islands and Indonesia; and continent-continent collision, such as the Himalayas.
Transform Boundary: Crust is neither created nor destroyed, horizontal displacement. Why does oceanic lithosphere almost always sink beneath continental lithosphere at convergent zones? Along which type s of lithospheric plate boundary are large earthquakes common? As one plate is being subducted beneath another, the overlying crust deforms.
Eventually the stress applied to the rock is greater than the strength of the rock causing the crust to fracture. Along which type s of lithospheric plate boundary are large volcanoes most common? Provide an example. How fast is this plate moving? Before people understood plate tectonics, what evidence led some scientists to believe in continental drift? ANSWER: Geographic fit of continents by matching coastlines across the Atlantic Ocean, match of rock formations across the Atlantic Ocean, match of ages of continental rocks across the Atlantic Ocean, match of fossils across the Atlantic Ocean, and glacial patterns.
What evidence confirmed seafloor spreading? The youngest ocean-floor basalt is at the ridge. Why are high volcanoes such as the Cascades found on the continents and in a row parallel to the continental margin?
Explain how the modern theory of plate tectonics developed in the context of the scientific method. The evidence for continental drift and additional data such as magnetic patterns in the ocean-floor were used to test the hypothesis of plate tectonics. How does the height of a mountain range compare with the thickness of the crust or lithosphere below the mountain? Relate this to the percentage of an iceberg above the water line. ANSWER: The height of an iceberg above the water line or a mountain range above the average continent is dependent on the difference in density between the submerged part of the iceberg or mountain and the surrounding water or mantle.
Natural hazards and disasters
About how high are the largest earthquake-caused tsunami waves in the open ocean? In December , a pair of closely related natural disasters killed tens of thousands of people. What was the initial cause of the event, not the one that apparently killed most of the people the general name for the type of event? Where, specifically, was that initial event? What was the specific kind of that initial event the variety of the general event noted in part a and the exact nature of it?
Natural Hazards and Disasters
A little technical at times By Matt on Feb 12, I used this book for an emergency management course. It is very technical, but it also covers a wide variety of natural hazards. I have a background in geology so I understood some of the processes described in the book. However, at times I felt that I needed a chemistry major. I was forced to buy this for class. By Christopher on Jun 04, I was forced to buy this for class. Yes it is a book, and yes it tells you about Natural Hazards and Disasters but you can get the previous version online for a fraction of the cost and the only real difference i saw was page numbers and the homework questions.
Natural Hazards and Disasters