EAS100 Lecture Notes - Lecture 31: Paleozoic, Thermohaline Circulation, Proterozoic

• School: University of Alberta
• Department: Earth and Atmospheric Sciences
• Course: EAS100
• Professor: Korhan Ayranci

Document Summary

Values and high temperatures in the middle cretaceous vs lower levels today. During the middle cretaceous period, sea level was 100-200m higher than now. Glacial deposits are widespread in late paleozoic rocks of the gondwana continents. Possibly dozens of glacial and interglacial intervals. Paleomagnetism indicates some were at low latitude. Difficult to reconstruct because of the polar ice caps that are present today. Snowball earth hypothesis suggests oceans were entirely covered by ice. Short term: 10 000 to 100 000 years. Long term: tens of millions to billions of years (milankovich cycles) Good correlation with orbital changes in the distribution of solar heat. Requires positive feedback mechanisms to explain overall cooling. Positions of continents and composition of the atmosphere must have influenced climate. Precession of the equinoxes: 23,000 year cycles. Tilt of the axis: 41,000 year cycles. Eccentricity of the orbit: 100,000 year cycles. Combined effect of orbital controls which affect distribution of solar energy over earth.