* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download (comprised of the continental crust and oceanic crust).
Survey
Document related concepts
Post-glacial rebound wikipedia , lookup
Deep sea community wikipedia , lookup
Age of the Earth wikipedia , lookup
Ocean acidification wikipedia , lookup
Geochemistry wikipedia , lookup
History of Earth wikipedia , lookup
Physical oceanography wikipedia , lookup
History of geology wikipedia , lookup
Oceanic trench wikipedia , lookup
Abyssal plain wikipedia , lookup
Mantle plume wikipedia , lookup
Supercontinent wikipedia , lookup
Geological history of Earth wikipedia , lookup
Transcript
The Structure of the Earth The planet Earth is comprised of a number of concentric layers. At the center is the core (a solid inner core and a liquid outer core). Surrounding the core is the mantle (similar to mafic minerals like olivine and the ultramafic peridotite). The outer most layer is the crust (comprised of the continental crust and oceanic crust). The Lithosphere Geologists use the term lithosphere to mean an outer Earth zone, or shell, of rigid, brittle rock. It includes not only the crust, but also the cooler, upper part of the mantle that is composed of brittle rock. The rigid, brittle lithosphere rests on top of a soft, plastic underlayer named the asthenosphere. The lithospheric shell consists of large pieces called lithospheric plates. The Lithosphere (a) Idealized cross section of the Earth's crust and upper mantle. (b) Details of the crust and mantle at the edge of a continent, including the types of rocks found there. Also shown are the lithosphere and asthenosphere. Continents and Ocean Basins The major relief features of the Earth are the continents and ocean basins.The continental masses consist of two basic subdivisions: (1) active belts of mountain-making and (2) inactive regions of old, stable rock. Continents and Ocean Basins Principal mountain arcs, island arcs, and trenches of the world and the mid-oceanic ridge. The Ocean Basin A typical ocean basin is characterized by a central ridge structure that divides the basin in about half. The midoceanic ridge consists of submarine hills that rise gradually to a rugged central zone. The continental margins are narrow zones which separate ocean crust from continental crust. From the ocean to the land it is comprised of the continental rise, then the continental slope, then the continental shelf. The Ocean Basin This block diagram shows an inner wedge of sediments beneath the continental shelf and an outer wedge of deep-sea sediments beneath the continental rise and abyssal plain. This schematic block diagram shows the main features of ocean basins. It applies particularly well to the North and South Atlantic oceans. Plate Tectonics The study of the motion of lithospheric plates and their interactions at their boundaries is plate tectonics. Tectonics refers to the breaking and bending of the entire lithosphere, including the crust. *See movie on plate tectonics in the geodiscoveries section of your text’s website. Plate Tectonics Diagram (a) is greatly exaggerated in vertical scale, and emphasizes surface and crustal features. Diagram (b) is drawn to true scale. Here the actual relationships between lithospheric plates can be examined, but surface features are too small to be shown. The Lithospheric Plates The rigid outer lithosphere is divided into a number of lithospheric plates of various shapes and sizes. The boundaries also differ according to whether plates are coming together (converging), moving apart (spreading) or moving alongside each other (transform). To explore the lithospheric plates further, visit the Animated Globe by clicking the globe icon on the menu bar. To return to this presentation, click "Previous". Tectonic Plate Boundary Relationships There are three major kinds of active plate boundaries: 1. Spreading boundaries - New lithosphere is being formed by accretion. 2. Converging boundaries - Subduction is in progress, and lithosphere is being consumed. 3. Transform boundaries - Plates are gliding past one another on a transform fault. *See movie on tectonic plate boundary relationships in the geodiscoveries section of your text’s website. Continents of the Past The distribution of continents was very different in the past than it is today. A single supercontinent, named Pangea, existed around 250 million years ago. It split up over time, and as the continents drifted we arrived at today’s pattern of land and sea. *See animation on continental drift/change in the geodiscoveries section of your text’s website.