GEOG 170A1 Lecture Notes - Lecture 14: Solar Wind, Outer Core, Geologic Time Scale
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14 Nov 2014
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GEOG 170- Earth’s Environment: Introduction to Physical Geography - Lecture 14:
Physical Parts of Earth
Monday 10/27/14
● We know from radio isotopic dating of rocks that Earth is about 4.6 x 109 (4.6 billion)
years old.
● Earth is an electromagnet. Earth’s magnetic field protects us from solar wind (a stream
of charged particles released from the upper atmosphere of the Sun). Earth’s magnetic
field ‘beats back’ the solar winds, producing the auroras.
○ List the sequence of layers in Earth, from the surface to the center:
■ crust
■ asthenosphere
■ upper mantle
■ lower mantle
■ outer core
■ inner core
● The principles of buoyancy and balance, when applied to Earth's crust, help explain
fluctuations in Earth's outer crust, a property known as isostacy.
○ The Geologic Cycle of Earth consists of 3 sub cycles:
■ hydrologic;
■ rock;
■ tectonic.
○ These 3 subcycles are the ‘architects’ of Earth’s landforms.
○ The Hydrologic Subcycle: the continuous movement of water on, above and
below the surface of the Earth.
○ The Hydrologic Cycle includes:
■ erosion
■ transportation
■ sedimentation.
○ The Rock Subcycle: the dynamic transitions through geologic time among the
three main rock types (sedimentary, metamorphic, and igneous).
○ The Tectonic Subcycle: The movement of Earth’s tectonic plates, which ‘forge’
mountains, fracture continents and move continents around.
● Earth’s continents were once a supercontinent—Pangaea. How do we know? Same
plant/animal fossils found on different continents today. Continents fit together like a
jigsaw puzzle. Magnetic fields of continental rock show original location. BIG POINT: No
one line of evidence proves plate tectonics—we need CONVERGING lines of evidence
—where different data all reach the same conclusion.