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1 Lec 20: 9 November 2011 Chap 9: The Earth. II. Changing Surface LAST TIME - Earth I. Overview of Earth as a Planet: Interior What’s inside, and how do we know? TODAY - Earth II. Earth’s Changing Surface Effects of gradual cooling of a planet 2 Kinds of Earth Crust Geological Activity Plate Tectonics NEXT - Surfaces of the Terrestrial Planets (Read Chap 11) THEN – Atmospheres and Climate of Terrestrial Planets Interactions Between Interior, Surface, Atmosphere, and Life Evolutionary, Cataclysmic, and Human-Induced Changes Global Properties of the Terrestrial Planets Mercury Venus Earth Moon Mars Mass 0.06 0.82 1 0.01 0.11 Diameter 0.38 0.95 1 0.27 0.53 Density (g/cc) 5.4 5.2 5.5 3.3 3.9 uncompressed... 5.2 4.3 4.4 3.3 3.8 Gravity 0.38 0.91 1 0.17 0.38 Albedo (%) 12 59 39 11 15 Atm. Pressure 0 88 1 0 0.01 Temperature (degrees K) 103-6 23 733 183-3 33 93- 403 133- 293 A bigger planet takes longer to cool down. Interiors of the Terrestrial Planets Heat and Thermal Energy Temperature is a measure of internal energy (kinetic and potential) Heat is “flow” of thermal energy from high temperature to low temperature 3 ways: Conduction , Convection , Radiation Why are planetary interiors hot? – gravitational contraction (mostly for Jovian’s) – primordial heat (accretion) – radioactive decay of heavy elements Two Types of Earth Crust 45% of surface up to 3.5 billion years old 20 - 70 km thick some sedimentary and metamorphic rock mostly granite (igneous) 55% of surface < 200 million years old 6 km thick some sediments (not sedimentary rock) basalt (igneous) Continental Oceanic granite solidified under high pressure; less dense than basalt Basaltic Lava Flows in Hawaii
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Page 1: Earth’s Changing Surface Effects of gradual cooling …neffj.people.cofc.edu › ASTR129 › Notes › lec20.pdfII. Changing Surface LAST TIME - Earth I. Overview of Earth as a Planet:

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Lec 20: 9 November 2011 Chap 9: The Earth. II. Changing Surface LAST TIME - Earth I. Overview of Earth as a Planet: Interior

•  What’s inside, and how do we know?

TODAY - Earth II. Earth’s Changing Surface •  Effects of gradual cooling of a planet •  2 Kinds of Earth Crust •  Geological Activity •  Plate Tectonics

NEXT - Surfaces of the Terrestrial Planets (Read Chap 11)

THEN – Atmospheres and Climate of Terrestrial Planets –  Interactions Between Interior, Surface, Atmosphere, and Life –  Evolutionary, Cataclysmic, and Human-Induced Changes

Global Properties of the Terrestrial Planets

Mercury Venus Earth Moon Mars

Mass 0.06 0.82 1 0.01 0.11 Diameter 0.38 0.95 1 0.27 0.53 Density (g/cc) 5.4 5.2 5.5 3.3 3.9 uncompressed... 5.2 4.3 4.4 3.3 3.8

Gravity 0.38 0.91 1 0.17 0.38 Albedo (%) 12 59 39 11 15 Atm. Pressure 0 88 1 0 0.01 Temperature (degrees K)

103-623

733 183-333

93- 403

133- 293

A bigger planet takes longer to cool down.

Interiors of the Terrestrial Planets

Heat and Thermal Energy

•  Temperature is a measure of internal energy (kinetic and potential)

•  Heat is “flow” of thermal energy from high temperature to low temperature

•  3 ways: Conduction, Convection, Radiation

•  Why are planetary interiors hot? – gravitational contraction (mostly for Jovian’s) – primordial heat (accretion) –  radioactive decay of heavy elements

Two Types of Earth Crust

•  45% of surface •  up to 3.5 billion years old

•  20 - 70 km thick •  some sedimentary and

metamorphic rock •  mostly granite (igneous)

•  55% of surface •  < 200 million years old

•  6 km thick •  some sediments (not

sedimentary rock) •  basalt (igneous)

Continental Oceanic

granite solidified under high pressure; less dense than basalt

Basaltic Lava Flows in Hawaii

Page 2: Earth’s Changing Surface Effects of gradual cooling …neffj.people.cofc.edu › ASTR129 › Notes › lec20.pdfII. Changing Surface LAST TIME - Earth I. Overview of Earth as a Planet:

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Kilauea Caldera

(Hawaii)

Two Types of Crust

•  45% of surface •  up to 3.5 billion years old •  20 - 70 km thick •  some sedimentary and

metamorphic rock •  mostly granite (igneous)

•  55% of surface •  < 200 million years old •  6 km thick •  some sediments (not

sedimentary rock) •  basalt (igneous)

Continental Oceanic

Both types “float” on the denser, plastic-like mantle.

Continents pile up higher, heavier, and less dense.

Geological Activity

•  earthquakes, volcanoes (several types), mountains (several types), island chains

•  constantly changes Earth’s surface

•  nothing left of “original” surface

•  driven by heat from Earth’s interior

•  plate boundaries : where the action is

Plate Boundaries Show Up When You Plot the Locations of Earthquakes or Volcanoes

Note: Video on your CD or the publisher’s web site.

Plate Tectonics

•  “Tectonics” - reaction of planetary surface to global forces

•  “Plates” (unique to Earth) –  lithosphere broken into 6 major and ~10

smaller plates – not just continents – no free space between the plates – plates move laterally, driven by convection in

mantle, by a few cm each year, with new material added in (mid-ocean) rift zones

Page 3: Earth’s Changing Surface Effects of gradual cooling …neffj.people.cofc.edu › ASTR129 › Notes › lec20.pdfII. Changing Surface LAST TIME - Earth I. Overview of Earth as a Planet:

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Relative Motions of Earth’s Plates

Plate Tectonics Examples

(see videos)

Mid-Atlantic rift

Volcanic Island

Himalayas (continental plates colliding)

Sanai (continental plates rifting)

Other Features of Plate Tectonics •  Super Continents

–  past.... –  future...

•  Hot Spots –  plate drifts across “plume”

that is fixed to mantle –  e.g. Hawaii –  there are hot spots on other

planets, too! •  Buildup and Evolution of

Continental Crust –  not subducted, less dense

than oceanic –  older than oceanic –  erosion and gradual

evolution

Bay Area in Metropolitan LA? I Hope Not! Other Features of Plate Tectonics

•  Super Continents – past.... –  future...

•  Hot Spots – plate drifts across “plume” that is fixed to mantle – e.g. Hawaii –  there are hot spots on other planets, too!

•  Buildup and Evolution of Continental Crust – not subducted, less dense than oceanic – older than oceanic – erosion and gradual evolution