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what was earths climate like in past

has been cooler - 600 million years ago late pre-cambrian - snow ball earth

sea ice extended to tropics

also warmer times eg greenhouse earth with dinosaurs - cretaceous - little or no ice


when did pangea break up

200 mill yrs ago


pre cyosphere

antarctica arrived during early cretaceous but not covered in ice sheet -94 mill yrs ago
used to be very warm

latitudinal gradient reduced


old v new boundary

old = cretaceous - teritiary (KT boundary)

now K-PG boundary - caused mass extinctions 65 million years ago


why did K-PG boundary cause mass extinctions

not 100% sure

old reason - volcanic eruptions, lava flows spread over 1500km killing 50% of all species

new reason - metrorite near mexico - rock boundary which contained 1000 times more iridium than upper and lower layers

veg grew back


when was cenozoic

65 mill yrs ago


what is tertiary now called

neogene and paliogene
2.5-65 mill yrs ago


what stage is at the end of neogene

quaternary 2.6 mill years ago to present


what is the quaterary stage divided into

holocene 0-11.7 thousand yrs

plesitocene - 11.7-2.6 million yrs ago


what is the eocene climate optimum

happened 50 mill yrs ago

antarctica had rich forests

london warmer crocs


what is palaeocene -eocene thermal maxiumum

55.5 mill yrd ago

large amounts of carbon ocean

temp incrase by 7 degrees in just 10,000-20,000 yrs

polar waters were > 20 degrres


eocene to oligocene why was there a cooling

cooling of antarctica ice sheet - opening of passages

cooling indicated by heavy oxygen isotope


lower atmospheric levels of co2 which got to a tipping point that creates icesheets - 500ppm this shows that if we go above this then we may lose ice sheets and go back to grrenhouse earth


what is the mid miocene climatic optimum

17-14.5 mill years ago

higher co2 levels and temp


temps up by 7 degrees

larger grassland areas


what is the pliocene

3.3 - 3 mil yrs ago
warm wet period + 3 dgrees


different veg here


what is the quaternary period

2.6 mill yrs ago

high frequency of climatic oscillations

intesnity of cold and glacial periods

cyclic changes of cold glaciers and warm interglacials


stratigraphic correlations

even no = cold/glacial eg Lat glacial maxium that happened 20,000 yr ago

odd no= warm periods interglacial eg oliocene today