They combine at irregular intervals the average is

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 0 years Discussion: Perihelion and Aphelion 25,700 years One More Point On This One • The orbital affects that Milankovitch suggested as a partial cause for ice ages each have a different period. • They combine at irregular intervals • The average is about 100,000 years but that is ONLY an average Earth’s Past Ice Ages Earth’s (oldest on bottom) • Tertiary- Quaternary cooling – Pleistocene 1.8 mya • None in Mesozoic • Late Pennsylvanian & Permian Ice covered part “Gondwana” (South Africa, South America, India, Australia, Antarctica) • Ordovician glaciation – Area that is now the Sahara at South Pole • PreCambrian Tillites (Lithified Till) At least three episodes. Interesting examples: – 750 mya ice from poles to tropic “SNOWBALL EARTH” – Oldest 2.8 bya Permian Glaciation – Gondwana Tillites Permian Poorly Sorted Unstratified Cenozoic Cooling Cenozoic The Late Tertiary and Quaternary oxygen isotope record measured in marine fossil shells Evap. water and CO2 during glacial time removes 16O to glacier ice leaving 18 O in oceans for CaCO3 shell Pleistocene Glaciation Pleistocene • • • • • Since 1.6 mya – more than 30 advances and retreats In 4 large scale pulses. Latest retreat 10,000 years ago Laurentide Little ice age 700 to 150 years ago. Sustained warming since 1850 Foraminifera tests - Ice Age Foraminifera Wisconsinan Illinoian > 30 pulses in 4 or so major groups Kansan Nebraskan Evap. water and CO2 removes 16O to 18 O in oceans warm Also spiral direction & diversity dep T during glacial glacier ice leaving for CaCO3 shell cold Continuous Ice Sheet 20 kya then warming Continuous Scoured 30 M below sea-level Cold pulse from about 1300 to 1850 AD (The so-called “Little Ice Age”) (The Climate has been warming since then. Discussion: Global Warming Worldwide melting, Worldwide regardless of cause, releases CO2 and H2O and exposes dark land. The atmosphere receives and holds more heat, and temperature rise. and Athabaska Glacier, Columbia Icefield, W. Canada End of Glaciers End...
View Full Document

This document was uploaded on 01/26/2014.

Ask a homework question - tutors are online