GEOS 170A1 Lecture Notes - Lecture 22: Last Glacial Maximum, Equinox, Geologic Time Scale

• School: University of Arizona
• Department: Geosciences
• Course: GEOS 170A1
• Professor: Randall Richardson

Document Summary

Precession (wobble of earth on its axis) The earth spins on its axis once every___: The earth is closest to the sun in ___: Seasons are due to the tilt of earth"s rotation axis- Tilt varies from ~21. 5 to 24. 5 degrees. Orbit becomes more or less elliptical (eccentricity) Rotation axis wobbles or precession (of the equinoxes) Seasons on a planet whose rotation axis is not tilted would be ___ a planet with a tilted axis: The planet without a tilted axis would not have seasons. Answer: the planet without a tilted axis would not have seasons. They are periods of geologic time when glaciers advance part of the time (glacial time) and retreat (interglacial) This ice age has been going on for the last ~2 million years. Geologic deposits, e. g. glacial, dust, fossils, pollen, pack-rat middens. See bubbles that preserve the atmosphere when the snow fell to make that piece of ice. Many glacial (colder) and interglacial (warmer) cycles.