Topic 2 - Glaciation EQ1 Flashcards
Explain the Pleistocene glaciation?
- roughly every 200-250 million years there are major periods of ice activity
- most recent is Pleistocene epoch of the quaternary period which lasted 2 million years
- led to significant fluctuations in global temperatures (led to glacial and interglacial period)
Outline what happens during glacial periods?
Climate cools significantly allowing precipitation to fall as snow - led to formation and growth of huge ice masses
- ice masses spread south over large parts of Europe, Asia and North America
Explain the position of ice during the extent of the Pleistocene epoch?
- about 20,000 years ago - vast ice sheets covered much of North America and Europe
- extensive glaciers and ice caps especially in mountainous regions - led to decrease in global sea levels (130m)
- ice extended over much of the UK - southern most remained ice-free
Outline the 3 main characteristics of the Pleistocene epoch?
- not single ice age - temperatures fluctuating allowing ice advances and retreats (50 interglacial cycles)
- extent of ice advance during each glacial was different
- were fluctuations within each major glacial - most recent stadial in British isles was Loch Lomond stadial (marked end of epoch)
Explain what stadial and interstadials are?
Stadials - relatively short-live pulses of ice advance (most recent was Loch Lomond)
Interstadials - warmer periods characterised by ice retreats
What can be concluded from the characteristics of the Pleistocene epoch?
- medium and large scale glacial erosional landforms are likely to be the result of several glacial advances
- depositional features tend to be the result of conditions and processes at work during the most recent glacial-interglacial cycle
Give 2 long term causes of climate change?
- Milankovitch cycles
- plate tectonics
Outline an explain how Milankovitch cycles can explain climate change?
Changes in earth’s orbit around sun seen as primary cause of the oscillations between glacial and interglacial conditions - looks at eccentricity cycle, precession and obliquity cycle
Over 100,000 year period when they all combine it causes major temperature changes (0.5 and 1 degrees) affecting glacial ice volumes
Explain the quaternary ice age, what are the two epochs?
5 known ice ages in earths history - most recent is the quaternary ice age (started approx 2.6 mill years and extends to present day)
- divided into Pleistocene (12,000 years ago) and Holocene epoch (started 10,000 and continues today)
Explain the obliquity cycle aspect of Milankovitch’s theory for causes of climate change?
Tilt of earth’s axis varies between 21.5 and 24.5 degrees - changes every 41,000 years - which affects the severity of the seasons
Explain the eccentricity cycle aspect of Milankovitch’s theory for causes of climate change?
Shape of earth’s orbit varies from circular to elliptical over period of 100,000 years - earth receives less solar radiation in elliptical orbit, characterised by glacial period
Explain the precession aspect of Milankovitch’s theory for causes of climate change?
Earth wobbles as it spins on its axis - affects whether the northern hemisphere is tilted away or towards the sun - happens every 21,000 years
- affects intensity of seasons
Outline and explain how positive feedback can increase warming?
Melting of ice cover by carbon dioxide emissions decreases albedo - methane is emitted as permafrost melts (increases greenhouse effect) causes rise in temperature leading to enhanced rates of calving and melting - loss of more snow cover further reduces surface albedo and decreases reflectivity of solar radiation - enhancing warming
Outline and explain how positive feedback can increase cooling rates?
Small increase in snow raises surface albedo so more solar energy is reflected back into space, leading to cooler temps - allowing more precipitation to fall as snow/ice
Outline and explain how negative feedback can decrease cooling rates?
Increasing global warming leads to more evaporation - pollution from industrialisation adds to global cloud cover, increasingly cloudy skies could reflect more solar energy back into space
- global warming could be less intense due to global dimming
Outline and explain how negative feedback can decrease warming?
Ice sheet dynamics can disrupt thermohaline circulation - warming water in arctic disrupts ocean currents, less warm water from gulf stream is drawn north which could lead to global cooling in Northern Europe
Explain how plate tectonics can lead to climate change?
- start of quaternary ice age linked to changing position of the continents due to tectonics
- NA and SA plates collided, re-routed ocean currents which now forced the warm Caribbean waters towards Europe, creating the Gulf Stream
- Gulf Stream transported extra moisture into artic atmosphere which fell as snow building Greenland ice sheet
Give 2 short term causes of climate change?
- variations in solar output
- volcanic emissions
Explain how variations in solar outputs can lead to climate change?
Sunspots are caused by intense magnetic activity in sun’s interior - increase in sunspots suggests sun is more active, and giving of more energy
- vary over 11 year period
Explain how sunspot activity has been linked to the little ice age?
Evidence suggest that the little ice age may have been triggered by volcanic emissions and variations in solar output - observations of the sun during the little ice age indicate very little sunspot activity on sun’s surface
Explain how volcanic emissions can lead to climate change?
Most significant impact of volcanic eruptions on the climate is the injection of large quantities of sulphur dioxide gas into the atmosphere
- remains in atmosphere for up to 3 years - forming sulphate aerosols which increase reflection of suns radiation back into space (albedo effect)
Give evidence for volcanic emissions affect on climate change?
Indonesian mount tambora (most powerful volcanic eruption recorded in history) - accounts of very cold weather were documented in subsequent year in many regions (lasted 5 years - short period)
- originally believed to be a result of the ash emitted into the atmosphere which blocked suns radiation however the ash returns to the surface within a few months
Explain what the lock Lomond stadial was?
significant period of climatic cooling that occurred towards the end of the last glacial period (Pleistocene epoch - about 12,000 years ago) - led to formation of ice caps in Scottish highlands which flowed outwards, glaciers in Lake District
Explain 2 causes of the Loch Lomond stadial?
- freshwater discharge from NA ice sheets - disrupted THC - cut of poleward heat transport from Gulf Stream
- impact hypothesis - asteroid impact could have triggered cooing - presence of extra-terrestrial material in sedimentary rock record