Lesson 17

Lesson 17 - Module E. Planetary Engineering: Mesozoic...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Module E. Planetary Engineering: Mesozoic Tectonics Lesson 17: Plate Tectonics 101 Introduction Plate Tectonics is the "Grand Unifying Theory" that explains the relationships between a wide range of processes going on within the Earth. The concept of Plate Tectonics grew out of the Theory of Continental Drift , which itself was based on the observation by Alfred Wegener in 1915 that some of the continental land masses seemed to fit together so well that it seemed inconceivable that they had not originally been joined and subsequently drifted apart. The Theory of Plate Tectonics The Theory of Plate Tectonics postulates that: 1. The Earth's surface consists of a number of lithospheric plates that include both the crust (continental or oceanic) and the immediately underlying portion of relatively cold and rigid upper mantle. 2. These plates are presently moving around on the surface of the Earth, and interacting with one another in various ways. Figure A-3. The Major Lithospheric Plates The layer of the Earth we live on is broken into a dozen or so rigid slabs (called tectonic plates by geologists) that are moving relative to one another. Map from the U.S. Geological Survey. Notice that some of the lithospheric plates consist partly of continents and partly of ocean floor. For example, the North American plate consists of the main North American continent, plus the western half of the Atlantic Ocean basin. Similarly, the Indian-Australian plate includes continental rocks that make up India and Australia, but also includes a vast extent of oceanic floor.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Plate motion Figure E-1. Average Rate of Motion and Relative Motion of the Earth's Tectonic Plates A schematic map of the global tectonic activity of the past 1 million years. Thin black arrows indicate spreading rate and direction in cm/year. Image from NASA . These plates are moving across the surface of the Earth in seemingly random directions and at different rates. The thin black arrows in the diagram show the relative plate motions of two adjacent plates, and the numbers are the rate at which the adjacent plates move with respect to one another at that particular point. Note that the rates (2 to 18 cm/yr) are quite slow, but it is easier to comprehend their meaning when we convert the rates from cm/yr to km/million years, which is the same as mm/yr. So for example, a rate of 10 cm/yr converts to 100 mm/yr, or 100 km/million years. With the perspective of geological time in terms of millions of years, rates of 100's of km/million years mean that entire oceans can be destroyed in just a few tens of millions of years. Significance of plate tectonics You're probably thinking, "So what? Why are plate tectonic processes so important?" Well, the answers are three-fold: 1. Almost all earthquakes, and most volcanoes, occur where lithospheric plates are interacting with one another; 2. Most of our main mineral and hydrocarbon resources occur in very specific tectonic settings; and 3. Plate tectonic processes going on at depth are almost entirely responsible for
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/18/2011 for the course EOSC 116 taught by Professor Randell during the Winter '09 term at UBC.

Page1 / 15

Lesson 17 - Module E. Planetary Engineering: Mesozoic...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online