NATS 1740 Chapter Notes -Impact Crater, Lunar Mare, Plate Tectonics

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Published on 13 Apr 2013
School
York University
Department
Natural Science
Course
NATS 1740
Professor
Chapter 7 Earth and the Terrestrial Worlds
7.1 Earth as a planet
Surfaces of the 5 terrestrial planets all looked similar when they were young
All 5 made of rocky material that condensed in the solar nebula
All 5 were impacted on by objects
Mercury
Covered in craters except in areas with volcanoes
Venus
Covered in thick atmosphere with clouds that hide its surface from view
Has volcanoes
Mars
Has the largest volcano and canyon
Why is earth geologically active?
- Surface is being constantly changed
Interior Structure
Core: highest density material consisting of metals like sickle, iron
Mantle: rocky material of moderate density (mostly minerals)
Crust: lowest density rock such as granite and basalt
Lithosphere: outer layer of cool rigid rock
Differentiation and Internal Heat
Differentiation: results in layers made of different materials
- Earth and the other terrestrial worlds were once hot enough inside for their interiors to
melt, allowing material to settle into layers of differing density
Internal heat and geological activity
Convection: process which hot material expands and rises while cooler material
contracts and falls
- Larger planets retain internal heat much longer than smaller ones and this heat drives
geological activity
The Magnetic Field
- Earth’s magnetic field is generated by the motions of molten metal in its liquid outer core
Magnetosphere: protective bubble that surrounds our planet
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What processes shape the earths surface?
Impact cratering: excavation of bowl shaped impact craters by asteroids or comets
crashing into a planet
Volcanism: eruption of molten rock or lava
Tectonics: disruption of a planets surface by internal stresses
Erosion: wearing down or building up of geological features by wind water ice
Virtually all geological features originate from impact cratering, volcanism, etc.
Impact cratering
- Travel at 40,000 250,000 km/h
- Like all terrestrial worlds, earth was hit by impacts when it was young but most ancient
craters have been erased by other geological processes
Volcanism
- Earth’s atmosphere and oceans were made from gases released from the interior by
volcanic outgassing
Outgassing: water and gasses are trapped beneath the surface, later erupt releasing some
of the gas into the atmosphere
- Our atmosphere is 77% Nitrogen
Tectonics
Plate tectonics: plates that move under, over and around each other
- Tectonics and volcanism generally occur together because both require internal heat and
therefore depend on a planets size
Erosion
- Erosion can both break down and build up geological features
- Much bigger role on earth than any other planet
How does Earths atmosphere affect the planet?
- Our atmosphere is 77% nitrogen and 21% oxygen and rest other gasses
Surface protection
- Ozone absorbs the suns dangerous ultraviolet radiation while xrays are absorbed by
atoms and molecules higher up in the atmosphere
- Ozone located in stratosphere
The greenhouse effect
- Our atmosphere traps additional heat making the earth really warm
- The greenhouse effect keeps earths surface much warmer than it would be otherwise
allows water to stay liquid over most of the surface
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Document Summary

Surfaces of the 5 terrestrial planets all looked similar when they were young. All 5 made of rocky material that condensed in the solar nebula. All 5 were impacted on by objects. Covered in craters except in areas with volcanoes. Covered in thick atmosphere with clouds that hide its surface from view. Core: highest density material consisting of metals like sickle, iron. Mantle: rocky material of moderate density (mostly minerals) Crust: lowest density rock such as granite and basalt. Lithosphere: outer layer of cool rigid rock. Differentiation: results in layers made of different materials. Earth and the other terrestrial worlds were once hot enough inside for their interiors to melt, allowing material to settle into layers of differing density. Convection: process which hot material expands and rises while cooler material contracts and falls. Larger planets retain internal heat much longer than smaller ones and this heat drives geological activity.

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