Glaciers - Enquiry Question 1 Flashcards
Pleistocene period
A geological period from about 2 million years ago to 11,500 years ago, the early part of the quaternary which included the most recent age
Greenhouse conditions
Much warmer interglacial conditions
Interglacials
Warmer periods similar to present, i.e. greenhouse periods
Glacials
Cold, ice-house periods within the Pleistocene
Ice-house conditions
Very cold glacial conditions
Types of cold environments
- Polar
- Alpine
- Glaciers
- Periglacials
Polar environments
- Glacial environments are found in the high latitudes of the Antarctic and Arctic
- They are characterised by extremely cold temperatures (average annually of -30 to -40°C and low levels of precipitation)
Alpine environments
Glacial environments are found at high altitudes in mountain ranges in the mid-low latitudes, e.g. European Alps, the Himalayas and Andes
- They are characterised by high levels of precipitation and a wide temperature range with frequent freeze-thaw cycles
Glacier environments
These are slow-moving bodies of ice in valleys, which shape the landscape in both polar and alpine environments
Periglacial environments
- These environments do not feature glaciers, but are usually found next to glacial areas
- They are characterised by permafrost and occur in high latitude areas where seasonal temperatures vary above and below freezing point, e.g. Siberia, Alaska and northern Canada
- Can be 3°C to -50°C
- Low biodiversity
What are the longest span of geological time?
Eons (typically around 1 billion years old)
What are the second longest span of geological time?
Eras
Ice Age/Pleistocene epoch
The Pleistocene epoch is often known as the ice age as it contained 50 glacial-interglacial cycles and glacials reached their furthest extent in this time
Devensian
The last glacial maximum is known as the Devensian which was 18,000 years ago
What was the last UK glacial advance?
- The last UK glacial advance was called the Lock Lomond Stadial which was 12,000 to 10,000 years ago and marked the end of the Pleistocene epoch
The UK is now called a relict glacial environment. What is meant by this?
It no longer experiences glacial conditions but it does display evidence of the Pleistocene glaciation period
How many years ago was the start of the Pleistocene?
2.6 million years ago
The Devesian glacial ended how many years ago?
18,000 years ago
The end of the Pleistocene/start of the Holocene was how many years ago?
11,500 years ago
How long did the Loch Lomond Stadial last?
10,000-12,000
Long term causes of climate change
- Continental drift
- Eccentricity of the orbit (Milankovich cycles)
- Axial tilt
- Wobble
Short term causes of climate change
- Variations in solar output/sunspots
- Volcanic causes (eruption theory)
Continental Drift
3 million years ago, the North and South American tectonic plates collided. This re-routed the ocean currents to that warm Caribbean waters were forced northwest, creating the Gulf Stream
Eccentricity of the orbit
The shape of the Earth’s orbit varies from circular to elliptical over 100,000 year cycles. The Earth receives less solar radiation in the elliptical orbit when the Earth is farthest from the Sun (a position known as the aphelion)
Axil tilt
The tilt of the Earth’s axis varies between 21.5° and 24.5° over 41,000 year cycles. This changes the severity of the seasons
Wobble
The Earth wobbles as it spins on its axis, which means that the season during which the Earth is nearest to the Sun (a position known as the perihelion) varies. At present, the northern hemisphere winter occurs in perihelion. i.e. milder conditions than previous winters in aphelion. This varies approximately 21,000 year cycles, resulting in changes in the intensity of the seasons
Variation in solar output
The dark areas of the Sun (sunspots) are cuased by intense magnetic activity in the Sun’s interior. An increase in the number of sunspots means that the Sun is more active and giving off more energy. They appear to vary over an 11 year cycle
Volcanic causes
Large eruptions can eject huge volumes of ash, sulfur dioxide, water vapour and carbon dioxide into the atmosphere (volcanic aerosols) which are globally distributed by winds. This aerosol blocks the Sun’s radiation, cooling the Earth. The ash tends to settle back on Earth within a few months, however the sulfur dioxide gas can remain in the atmosphere for up to 3 years, which reflects the radiation back into space
Loch Lomond Stadial (the Younger Dryas event)
- Ice sheets began retreating about 18,000 years ago, with rapid deglaciation by 15,000 years ago (late glacial interstadial) with similar temperatures as today leading to widespread distribution of deciduous woodlands across Europe
- However, around 12,500 years ago the temperatures plunged downwards and, by 11,500 years ago, glacial conditions occurred with temperatures 6-7°C lower
- Glaciers re-advanced in many parts of the world including the formation of ice caps in Scottish Highlands, from which cirque and valley glaciers flowed outwards, with smaller areas of cirque glaciers in the Lake District and North Wales
The Little Ice Age (Holocene)
Between 1350 and 1900, conditions were slightly colder - perhaps on average by between 1.0°C and 2.0°C - than at present over much of the globe
- Between 1550 and 1750 there was a low trough of very cold conditions, known as the Little Ice Age, which occurred globally
Impacts of the Little Ice Age
- The widespread abandonment of upland farms in Scandinavia and Iceland
- Many glaciers in Europe re-advanced down valleys; the Little Ice Age was a period of predominantly positive net mass balance leaving prominent terminal moraines from which the glaciers subsequently retreated, but often at different dates/ times around the world
- Arctic Sea ice spread further south with polar bears seen frequently in Iceland
- Rivers in the UK and lowland Europe, and New York habour, froze over
- Curling developed as a national sport in Scotland as there were so many frozen lakes and rivers
- In Chamonix Valley, France (near Mont Blanc), farms and villages were lost to the advancing front of a nearby mountain glacier
- Crop failures in N. Europe
- Increased cases of famine, disease and child mortality in Europe (17th-19th century)
- In London, where the Thames had frozen over, winter carnivals/markets were held
Cryosphere
- The cryosphere consists of ice sheets and glaciers, together with sea ice, lake ice, permafrost and snow cover
- Mass and energy are constantly exchanged between the cryosphere and other major components of Earth systems; the hydrosphere, lithosphere, atmosphere and biosphere
Glaciers
- Glaciers are large bodies of ice which flow downhill under the influence of gravity
- Some are land based and their base is at or above sea level e.g. Mer de Glace flows from Month Blanc in the Alps, or glaciers flowing from the Rocky Mountains
- Others are marine bases, where the base is below sea level, e.g. the West Antarctica Ice sheet - which is 2000m below sea level, and is actually frozen to the sea bed
Warm based glacier
Occur in high altitude areas outside the polar regions e.g. the Alps. The temperature of the ice is often close to zero and mild summer temperatures cause melting
Cold based glaciers
These occur in polar glacial environments such as Greenland and Antarctica. These glaciers are frozen onto the bedrock below and melting only occurs on the surface in the summer months
Ice sheet
- Complete submergence of regional topography; forms a gently sloping dome of ice several kilometres think in the centre
- 10-100,000 sq km
