Kind: captions
Language: en
despite being above the Arctic Circle
Lake alga chicken has never been covered
by glaciers which means that when
sediment all that material floating are
living in the water settled on the
bottom of the lake it formed layers that
have remained undisturbed so you start
to accumulate sediments at the bottom of
the lake
but also what's accumulating in there is
organic matter so anything that's living
on the landscape can get washed into the
lake so all of those elements give us a
snapshot of what the ecosystem was like
and that ecosystem then can tell us
something about the climate at the time
what pollen counts from the past million
years show us is that the climate around
Lake alga Gagan has been oscillating or
changing from warmer periods to colder
periods each period lasting thousands of
years it's like a detective story doing
this work and just like solving a
mystery it's best when you have multiple
lines of evidence all pointing to the
same conclusion we can actually take
pollen counts and combine it with data
from diatoms and those mammoths poop
eating fungal spores to understand how
this lake has changed over the last
million years and we can combine the
lake data with similar course from
around the world all of those elements
give us a snapshot of what the climate
was like for the last thirty four
million years Earth has actually been an
ice house with ice at at least one of
the poles year-round and here's the big
lesson that Lake alga geekin has taught
us that even within an ice house the
temperature oscillates between very cold
periods called glacials with ice sheets
extends down over the continents and
warmer interglacial periods like today
when there is still ice but it's
confined to the poles the big question
is why it turns out that what drives
glaciation for the most part are three
changes in Earth's orbit around the Sun
the orbit can be more oval or more
circular the tilt of the planet can
increase or decrease and Earth's axis
wobbles like
these changes occur over tens to
hundreds of thousands of years and they
affect how heat from the Sun warms
different parts of the planet but that's
only part of the story because the
orbital cycles and the position of the
earth can't explain why the changes in
temperature are so extreme and why
they're global so what else is going on
here you're about to find out
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