Friday, February 3, 2012

Lecture 8

Lecture #8: Friday, February 3, 2012

Terraces
• Different levels
• Took samples and tested using radioactive dating method (thorium)
• Minerals capable of self reversal were rare in lava
• Purpose was dating to find when ice age happened
• Evidence for it in two cores in the Pacific Ocean
• Beginning date of Plasticine of 1.8 million years ago
• Czek was not glaciated during last ice age, it was a tundra
• Lag time 8000 years
• Lag time precession were symmetrically related to the dates of those precessions
• Most important: dec 10, 1976: variations in earths orbit

• Ice age changed global land scape
• Vegetation had to migrate
• Glacial period comes through and wipes out everything that was there before
• 21000-5700 years ago it is largely gone
• land bridge to cross over into the Americas

Landscape Changes and New Land Features
• Terminal marane: pile of till that marks furthest extent of ice sheet or glacier
• Esker: formed where streams flowed under the glaciers usually forming a tunnel in the glaciers
• Rock that has been formed by glaciers
• Valley head that has been carved out by a glacier to a round shape

Eustacy and Isostacy
Great Lakes, Lake Champlain
• Eustacy: global rise in sea level which occurs due to fluctuations in the polar ice caps
• Isotacy: LOCAL, Pulls down on stuff around it, when you remove the glacial ice the crust bounces back
• Isostatic rebound of the lithosphere in response to the weight of the ice sheets being removed
• Response of the receding ice sheets
• Champlain Sea:
• Jokullhlup:
• When flood water (Lake Erie and Lake Ontario combined) gets carried along into
• www.hugefloods.com/laksmissoula.html

Homo Sapien Migrations
• 12000 years ago into Canada and the US
• 11000 years ago in South America
• 30000 years ago in South East Asia