Environments Flashcards
Where are cold environments found?
High latitudes and high altitudes. E.g. Arctic and Antarctic circles and lower latitudes but high altitudes like the Himalayas
3 types of cold environments:
Glacial - permanently below 0°c
Peri-glacial - on the edge of glacial environments with a bit of melting and thawing in summer. Only found in northern hemisphere because of greater landmass at high latitude.
Alpine - mountainous areas with snow and ice in winter and lots of melting and thawing in summer. (Alps)
Ice age definition
When a significant proportion of the earths surface is covered in ice
Inter glacial and stadial periods
Inter glacial periods are the warmer periods of an ice age and within them you get stadials such as the little ice age (1515-1815)
Glacial and inter-stadial periods
Glacial periods are the colder periods and within these, there are inter stadials which are warmer sub-periods.
Quaternary ice age
We are in the quaternary ice age now and there have been two main periods:
Pleistocene - 1.8 million years ago - 10,000 years ago
Holocene - 10,000 years ago - now
How do we know that climate has changed? (7 ways)
Church records Carbon dating Sea floor analysis Ice core analysis Tree rings Fossil remains Landscapes
Sea floor analysis explanation and method
The ocean contains isotopes of oxygen, O16 and O18.
O16 evaporates more easily and returns to the ocean as precipitation, thus keeping the ratio constant.
However in cold periods, it remains on the land as snow or ice thus changing the ratio.
Clean creatures make their shells out of oxygen so in colder periods, their shells contain more O18.
These shells become sedimentary rock which can be analysed.
How landscapes show climate has changed
Landforms such as drumlins and moraines indicate ice cover and direction of flow in the past
How does ice core analysis show that climate has changed?
Ice cores can be drilled in Antarctica and oxygen ratios can be measured in similar ways to sea floor. This provides accurate information about previous climates
how does carbon dating show that climate has changed?
Organic matter contains equal isotopes of C12 and C14.
C14 decays and C12 doesn’t.
By measuring the ratios of Carbon isotopes, you can tell how long the organism has been dead for.
You can take an educated guess for what the climate was like by looking at characteristics of the organism
How can tree ring analysis show that climate has changed?
The wider the tree ring, the warmer and more humid the climate was.
This indicated which years were warmer and colder.
Only max 4,000 years and doesn’t give exact temperatures.
How can fossil remains show that climate has changed?
Tells us about the type of animal in particular places and can indicate a climate at that time.
Milankovich cycles
Eccentricity - orbit shape - 100,000 years with a sub cycle of 40,000 years
Obliquity- axial tilt - 41,000 years
Precession - wobble of the axis - 26,000 years
Why has climate changed? (6 reasons)
Milankovich cycles Sunspot activity Volcanic activity Landmass changes (Current global warming)
Why has sunspot activity caused climate to change?
The sun flares up in parts generating more heat and reduction of sunspots leads us into a colder period (little ice age)
Tends not to give more than 2°c difference
Why do volcanic events cause climate change?
Ash rises up into the atmosphere and circulates round the globe and acts like a sheet blocking out the sun and cooling the environment
Why do landmass changes cause climate change?
A large land mass surrounded by one ocean can retain heat better than lots of smaller land masses because land is warmed quicker by the sun
Effects of he little ice age (1550-1850)
Bought colder winters - canals and rivers froze (Thames)
Glaciers advanced and wiped out villages in the alps
Sea ice extended out from Iceland
Greenland was cut off due to ice
Crops were destroyed
Scale and location of ice
Ice sheets- vast expanses of ice, over 1km thick.
Ice caps- smaller masses of ice often associated with mountain ranges.
Ice fields- areas less than 50,000 square km.
Glaciers
Types of ice flow
Basal flows: Extending Compressing Surges Creep Rotational
Non basal flow:
Internal
Compressing flow
Occurs when gradient is low
Speed of ice decreases and ice thickens
Erosion is high
Extending flow
Occurs when the gradient is steep
Ice moves faster and thins
Erosion is less here
Surges
When a glacier moves very rapidly (up to 100 times faster than usual)
Due to excess meltwater
Creep
When ice meets an obstacle, it becomes pressurised and behaves like a plastic and flows around the obstacle.
Then it returns to normal flow
Rotational flow
When ice pivots around a central point in a rock basin, widening and deepening it.
Internal flow (deformation)
This happens in both temperate and polar glaciers.
Ice crystals deform to become streamlined in the direction of flow.
They slip and slide past each other very slowly.
Basal flow
Where meltwater, resulting from pressure and friction, allows ice to move more rapidly.
Only happens in temperate/alpine glaciers.
Where is the fastest flow in a glacier?
Centre (looking from above)
Top (looking from the side)
Formation of ice
As snow falls, it compacts to form ice in a process called alimentation.
Over time, oxygen it squeezed out to give it a blue colour.
Known as firn or névé.
Snow lines
Can only happen at the equator at 6,000m and is symmetrical.
In the northern hemisphere, the snow line is north facing.
In the Southern Hemisphere, the snow line is south facing.
Types of glacier (temperate/alpine)
E.g. In the Alps
They melt in the summer and the meltwater acts as a lubricant and reduces friction.
Erosion, transportation and friction occur
Types of glacier (polar)
These occur when the temperature is permanently below 0°c.
Therefore NO melting occurs.
They are frozen to heir beds and movement is internal and slow.
Pressure melting point
Usually is similar to the temperature of the base so melting occurs.
But the temperature of the base of a polar glacier is much colder so NO melting occurs ever.
Positive and negative feedback
Negative feedback happens to keep a system stable in equilibrium.
E.g. More snowfall —> more ablation (melting).
Positive feedback exacerbates the change.
E.g. Environment cold so more snow, more of the suns energy reflected (albedo) so it gets colder…
