2 - Glaciation Flashcards
What is the Quaternary ice age?
The Quaternary ice age is the most recent ice age (out of 5) which started ~2.6 million years ago.
What two epochs is the Quaternary ice age divided into?
- The Pleistoscene, which lasted until 10,000 years ago
- The Holocene, which began 10,000 years ago and continues today.
What was the Pleistoscene eopch?
The Pleistoscene epoch (aka the Ice Age) was characterised by 50 glacial-interglacial cycles and glaciers reached their maximum extent during this time.
What was the Last Glacial Maximum?
The Last Glacial Maximum was when ice sheets were at their largest (~21,000 years ago). Most of Europe was periglacial (frequently thawing and freezing).
What type of glacial period is Earth currently in?
Interglatial
What are the three Milankovitch cycles?
- Eccentricity
- Obliquity
- Precession
How does Eccentricity cause long-term climate change?
-The shape of the Earth’s orbit becomes more elliptical, changing the amount of solar radiation the Earth receives.
- When the Earth is (relatively) further away from the Sun, it receives less solar radiation so a glacial period occurs.
- The shape of the orbit changes about every 100,000 years, which closely matches the glacial-interglacial cycle.
How does Obliquity cause long-term climate change?
The tilt of the Earth’s axis changes; the higher the tilt, the higher the temperature range between the seasons, affecting the climate.
How does Precession cause long-term climate change?
The Earth goes through long cycles of ‘wobbles’ on it’s axis, meaning different parts of the Earth go through phases of facing towards or away from the Sun. This means that as precession changes, the length of seasons changes, therefore changing the amount of snow and ice on the Earth’s surface.
What are two short-term factors leading to climate change?
- Variations in Solar Output
- Volcanic Eruptions
How do Variations in Solar Output cause short-term climate change?
Intense solar radiation is linked with the presence of sunspots. The amount of solar radiation reaching the Earth’s surface affects the climate (e.g The Little Ice Age corresponded to a time with no sunspot activity).
How do Volcanic eruptions cause short-term climate change?
Volcanic eruptions eject ash and carbon dioxide into the atmosphere.
While the gases also contribute to the greenhouse effect, the main effect comes from ash plumes and sulfur dioxide reducing insolation due to reflecting solar radiation back into space. This causes global cooling.
What was the Little Ice Age characterised by?
From 1300-1850 (during the Holocene) temperatures decreased by 0.5°C - 1°C across Europe and North America. Standing and flowing water like the River Thames froze, and glaciers advanced rapidly, displacing settlements.
What was the Little Ice Age caused by?
Scientists believe the cause was a combination of sunspot and volcanic activity.
What was the Loch Lomond Stadial characterised by?
Around 12,700 years ago, (during the Pleistocene) ice age conditions returned to some parts of the UK for around 1 millennium. UK winter temperatures fell and mountainous areas were exposed to wet weather conditions and were covered in ice.
What is the albedo effect?
Whre land and sea ice reflect solar radiation back into the atmosphere, creating cooler conditions, which allow more ice to form.
What does it mean if a glacier is in ‘dynamic equilibruim’?
If there’s the same amount of accumulation and ablation over a year, the glacier stays the same size and the position of the snout doesn’t change – the glacier is in dynamic equilibrium.
Explain how a positive feedback loop can cause a glacier to retreat.
If glaciers retreat, there is less ice, meaning less of the Sun’s energy is reflected and more is absorbed, so temperatures rise and glaciers retreat further. For instance, the Greenland Ice Sheet is in a positive feedback loop, and is losing mass increasingly rapidly.
