Quaternary Climate Change

• when was/is the quaternary period?

  from 2.58 million years ago until present day
• what is the quaternary period divided into?

  the Pleistocene and the holocene
• when was the last glacial maximum?

  24 thousand years ago
• roughly how long are cycles of glaciation?

  100,000 years
• what are glacial periods characterised by?

  more water locked up on land as ice and lower sea levels
• where are the tropics?

  30 degrees north to 30 degrees south latitude
• as the tropics are much warmer, what are they important for the energy balance?

  they are considered the earth's accumulation zone
• why are the tropics considered the earth's accumulation zone?

  they export excess solar energy to help warm the rest of the planet
• where is the intertropical convergence zone?

  between 20 degrees north and 20 degrees south of the equator
• what is the climate like in the intertropical convergence zone?

  very wet = most of earth's rainfall and rainforests are seen here
• why does the intertropical convergence zone see the most rainfall?

  air is warm around the equator, so less dense and rising. as air rises, it cools and loses buoyancy, meaning it is pushed north and south as it descends. this makes up the Hadley cell
• what is the refugia theory?

  that there are small pockets where it is possible for species to survive and grow during periods of adverse climatic conditions not favourable for their survival
• what was seen in Africa meaning that it was much wetter than it is today?

  the African humid period
• what caused the African humid period?

  the orbital force of precession
• what did the African humid period lead to?

  increased rainfall as there was a stronger African monsoon
• what was the result of the African humid period?

  a 'green sahara' and much more substantial lakes and rivers
• why was the African humid period so important for anthropogenic development?

  it increased water supply, allowed for the expansion of modern settlements and drove agricultural developments
• what caused megafauna to become extinct?

  the late quaternary extinction
• when was the late quaternary extinction?

  the end of the last glacial period, 12,500 years ago
• what is thought to have caused the late quaternary extinction?

  an interaction of hunting and climate change
• what suggests that the late quaternary extinction was caused by human hunting?

  Martin's overkill hypothesis
• what was the ground for Martin's overkill hypothesis?

  the largest losses occurs in the areas with the most people moving into them = extinction roughly matches with influx of population
• how would climate change have caused the late quaternary extinction?

  greater seasonality meant the megafauna could not adequately adapt
• aside from climate change and over hunting, what is a third hypothesis for the cause of the late quaternary extinction?

  that the faunas were disharmonious and fought / hunted each other into extinction