Lecture 21 - Ice Ages

Question 1

ice coverage during glacial periods

Answer 1

• northern continents have a lot of ice coverage (one continuous ice sheet) during glacial periods
• glacial periods do change equatorial climates as well but no ice sheets

Question 2

how does moving ice gouge the earth?

Answer 2

as glaciers move, sites are excavated because ice is pushing things to the side or pulls debris with it

ex: Madison rock, the great lakes

Question 3

ice age temperature changes in last 1 Ma

Answer 3

• 8 major glacial episodes
• periodicity of ~100ka
• last glacial maximum was ~26ka
• peaks of ice volumize characterize ice ages

Question 4

ice ages vs modern biomes

north america

Answer 4

during last glacial period - NA covered by Laurentide Ice Sheet

now
* diverse biomes across NA
* glacial areas push everything further south during glacial periods and condense other biomes in souther NA

Question 5

ice ages vs modern biomes

fossil pollen record

Answer 5

pollen is durable - protective coatings, preserves for thousands of years

Question 6

ice ages vs modern biomes

europe

Answer 6

similar situation to NA, less extensive ice sheet

Question 7

ice ages vs modern biomes

neanderthal existence in europe

Answer 7

• neanderthals first appeared in Europe 400ka
• continuously occupied until 40-30 ka
  so occupied many glacial periods
• clearly able to live in variety of environments, even inhospitable ones

Question 8

what controls the ice ages?

Answer 8

• milankovitch cycles - eccentricity (elongation = more time away from sun, drives pacing of glacial periods)
• suppression of thermohaline circulation
• feedback loops

Question 9

suppression of thermohaline circulation

Answer 9

• Younger Dryas
• during rapid warming at the end of last ice age - water from Lake Agassiz spills out into ocean and reduces salinity (fresh water, shuts down heat transfer that’s happening in thermohaline circulation

Question 10

why do glacial periods end abruptly?

Answer 10

positive feedback loop
* eccentricity cycles cause small amount of warming
* warmer oceans release CO2, increases greenhouse effect, increase tempreature

Question 11

glacial impacts on hominins

neanderthal hunting

Answer 11

• capable hunters of prime age big game - thrust spear usage
• mortality age profile of game doesn’t match large carnivores - went after species in prime instead of young/weak

Question 12

glacial impacts on hominins

dealing with change

Answer 12

• neanderthal hunting switched btwn red-deer dominant and reindeer dominant
• red-deer = woodlands, forested environments, temperature distributions
• reindeer = cold
• no problem switching to deal with requirements of hinting different animals during different periods

Question 13

glacial impacts on hominins

processing hides

Answer 13

extreme anterior tooth wear common for Neanderthal, consistent with hide processing

Question 14

summary

Answer 14

• living at temperate latitudes during glacial/interglacial cycles involved cultural and/or biological adaptation
• neanderthals exhibit many of these
• modern humans are more recent immigrants to temperate climates