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ENVIRONMENTAL SCIENCE

ENVIRONMENTAL SCIENCE. Chapter 3 The Dynamic Earth 3.1 The Geosphere. 3.1 The Geosphere Objectives. Describe the composition and structure of the Earth. Describe the Earth’s tectonic plates. Explain the main cause of earthquakes and their effects.

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ENVIRONMENTAL SCIENCE

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  1. ENVIRONMENTAL SCIENCE Chapter 3 The Dynamic Earth 3.1 The Geosphere

  2. 3.1 The Geosphere Objectives • Describe the composition and structure of the Earth. • Describe the Earth’s tectonic plates. • Explain the main cause of earthquakes and their effects. • Identify the relationship between volcanic eruptions and climate change. • Describe how wind and water alter the Earth’s surface.

  3. The Earth as a System • The Earth is an integrated system made of four major systems that constantly interact and affect one another. • Geosphere – solid part of Earth, the rocks, soil, and sediment • Atmosphere – envelope of gases that surround the Earth • Hydrosphere – all of the water on Earth • Biosphere – all of the living things (organisms) on Earth

  4. The Earth as a System • The majority of the geosphere is located beneath the surface of the Earth. • The average diameter of the Earth at the equator is 12,756 km. • Most of the molecules that make up the atmosphere are found in the lower 30 km of our atmosphere. • Oceans cover about 71% of the Earth’s surface. • The life, or biosphere can be found living from the bottom of the ocean to about 9 km above sea level – a total range of about 20 km.

  5. Discovering Earth’s Interior • The Earth’s interior cannot be studied through direct observation – the deepest well drilled is only about 12 km deep. • Scientists use seismic waves to study the structure of the Earth’s interior. • A seismic wave is altered by the material through which it travels. • Seismologists measure the speed and direction of seismic waves as they penetrate the Earth’s interior.

  6. Discovering Earth’s Interior • The Earth can be divided into three compositional layers. • Crust • Mantle • Core • These layers are made with progressively denser material closer to the Earth’s center.

  7. Discovering Earth’s Interior • The crust is a thin, outer layer of the Earth made almost entirely of lighter elements. • The crust makes up less than 1% of Earth’s mass. • Oceanic crust is 5 km to 8 km thick and made mostly of basalt. • Continental crust, mostly granite based, is between 20 km to 70 km thick.

  8. Discovering Earth’s Interior • The mantle, just below the crust, makes up 64% of the mass of the Earth. • The mantle is about 2,900 km thick and is made mostly of medium density rock. • The core, Earth’s inner-most layer, is composed of the densest elements and has a radius of about 3,400 km.

  9. Discovering Earth’s Interior • The Earth, based on physical properties, can be divided into five layers. • Lithosphere (15 to 300 km thick) a cool, rigid layer that includes the crust and the upper part of the mantle and is divided into large tectonic plates • The asthenosphere (250 km thick) is a plastic, solid layer of the mantle that flows very slowly and allows tectonic plates to move on top of it • Mesosphere – (2,550 km thick) the lower layer of the mantle between the asthenosphere and the outer core • Outer core (2,200 km thick) outer shell of Earth’s core made of liquid nickel and iron • Inner core – (1,228 km radius) sphere of solid nickel and iron at the Earth’s center

  10. Plate Tectonics • The Earth’s lithosphere is divided into large tectonic plates which glide across the underlying asthenosphere much like chunks of ice setting on a frozen lake. • The continents are located on tectonic plates and move around with them over time. • Much of the geologic activity that occurs at the Earth’s surface takes place at tectonic plate boundaries. • The formation of mountains and volcanoes, as well as violent earthquakes, are the result of the forces of tectonic activity.

  11. Plate Tectonics • There are three types of plate boundaries. • Convergent • Ocean – ocean collision • Ocean – continent collision • Continent – continent collision • Divergent • Transform

  12. Earthquakes • A fault is a fracture in the bedrock along which movement has occurred. • When rocks are under stress along a fracture, they can sometimes snap as the stress is released. • The vibrations which travel through the ground as a result of this release of energy are known as earthquakes. • Earthquakes occur all the time, but most are not felt (only detected by instrumentation).

  13. Earthquakes • The amount of energy released by an earthquake can be quantified and compared on the Richter Scale. • The smallest magnitude that can be felt is 2.0 and the largest magnitude ever recorded was 9.5. • An increase in magnitude of whole number indicates the release of 31.7 times more energy than the number below it. • The majority of earthquakes occur along plate margins.

  14. Earthquakes • Though earthquakes cannot be accurately predicted, risk for earthquakes can be better assessed. • Earthquakes can damage roads, gas lines, electrical supply, sewage, and even large buildings.

  15. Volcanoes • Volcanoes are mountains build from molten rock (magma and lava) and are often located near tectonic plate boundaries. • Most of the world’s active volcanoes on land are located on tectonic plate boundaries that surround the Pacific Ocean. • Volcanic eruptions can be devastating locally with gas and pyroclastic flows that can exceed 200 km/hr. • Ash from eruptions can also be carried in the atmosphere and travel far.

  16. Volcanoes • Volcanic eruptions can alter global weather conditions. • When Mt. St. Helens erupted in 1980, average global temperature dropped slightly.

  17. Erosion • The Earth’s surface is subject to the effects of weathering and erosion. • Wind and water are constantly working to remove and transport surface materials. • Water erosion, over time, can dramatically change the landscape. • For example, the Grand Canyon was created by stream erosion over time • Wind erosion is most evident in desert and beach areas.

  18. References • Earth’s Compositional Layers - http://www-cms.llnl.gov/s-t/extreme_chemistry.html • Earth’s Structural Layers - http://schoolscience.rice.edu/science/curricula/printpreview-noimage.cfm?CurriculaID=315 • Earth Structure Compared - http://elmo.shore.ctc.edu/ebaer/Geology%20101/tests/test1key.html • Tectonic Plates - http://www.stchas.edu/faculty/ewilson/Photos/Plates

  19. References • Earthquake Distribution - http://www.geology.uiuc.edu/~hsui/classes/geo116/lectures/earthquakes-demo.htm • Earthquake in San Francisco - http://www.geology.uiuc.edu/~hsui/classes/geo116/lectures/earthquakes-demo.htm • Tectonic Plate Boundaries - http://www.scarborough.k12.me.us/wis/teachers/dtewhey/webquest/nature/plate%20boundaries.htm • Pyroclastic Flow - http://www.geo.umn.edu/courses/1001/Summer_Session/SedImages.html

  20. References • Mt. St. Helens - http://geosciences.ou.edu/~msoreg/volcanoes/Mt_StHelens1.html • Death Valley Sand Dunes - http://www.beachdoctor.com/sethmedlin/Family%20Travel%20Death%20Valley%20April%202003.htm • Grand Canyon - http://www.evcforum.net/cgi-bin/dm.cgi?action=msg&f=7&t=162&m=1

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