Geo Interactions Flashcards
Interacting Processes: TECTONIC
What happens between the two plates? How much movement per year?
Indo Australian and Pacific Plates collide and push up the land mass. This plate tectonic movement occurs at a rate of 40mm per year.
Interacting Processes: CLIMATIC
- Uplift
- Air condense and fall
- Snow and glacial ice
Interacting Processes: EROSION, DEPOSITION, ETC
- Glacial features (carved)
- material transport
- new rock formed, uplift (ie, young gravel)
TECTONIC: Where are the convection currents?
Found in the upper mantle.
Heat (convection currents) move the crust around where the Indo- Australian and Pacific Plates collide.
TECTONIC: Why do the plates (Indo- Aus and Pacific) not subduct?
Because both sides are continental crust they do not subduct and both sides are forced upward pushing sedimentary greywacke and metamorphic schists up at a rate of 40mm a year.
(Technically this rate is faster, but at the same time the erosional processes discussed later are interacting with the landscape and
wearing it away.)
TECTONIC: How high would the Southern Alps be without erosion?
If not for erosion, the Southern Alps would be more than 23km high. This interaction along the Alpine fault creates faulting as the Alpine Fault ruptures every 300 years with a magnitude 8 quake pushing the land mass up in blocks. This can be seen in cuttings geologists explore in places like the Haupiri Valley.
CLIMATIC: What does the uplift mean for the Southern Alps?
The uplift means that the Southern
Alps rise to over 2500m in most
places (3724m at its highest point at
Aoraki/Mt Cook). This rise in land
alters the climate.
CLIMATIC: How does the wind blow? (Moist Westerly…)
Explain stages of the journey:
Moist Westerly winds blow over the vast fetch and then enter the Tasman Sea. As the moist air hits land, it is forced up and starts to condense and release moisture. At the coast near Fox, 3000mm falls. At the 1000m mark, 12,000mm falls. This creates deep V shaped gorges and fast flowing rivers such as the Waitaha and the fluvial erosion cuts into the land.
CLIMATIC: How do glaciers form? (In the Southern Alps)
What happens to snow as it builds up?
Snow falls above 2000m and does not melt away fast enough and so glaciers form. The process of glaciation is where snow falls accumulate in areas and build up
year after year.
The snow starts to compact and firm up and change to firn. When most of the air has been squeezed out after about 6 years, the snow flakes have become glacial ice.
EROSION, DEPOSITION ETC: What features are created by the glaciers (or carved out)?
These glaciers (eg Fox) then start to carve their way into the landscape creating various features such as horn peaks (Mt Aspiring), Aretes (Homer Saddle), and U shaped Valleys (Tasman).
EROSION, DEPOSITION ETC:
What happens when the large ice mass slides down the valley?
As the large ice mass, such as Franz
Joseph slides down the valley, moraine GRINDS against the valley and gauging out more greywacke and schist creating the distinctive U
shape.
EROSION, DEPOSITION ETC: What happens to materials after the ice mass carves out the valley?
Fluvial processes from the constant
(3000mm+ per year) then transport the material down the Waihao River and create outwash plains like the ones on the Western side of SH6.
EROSION, DEPOSITION ETC:
What happens at the same time as fluvial processes transport the materials? (and create outwash, etc)
hint: uplift… push land up…, new and softer rocks …
At the same time, uplift from
plate tectonics continues to push the land up.These newer and softer rocks and gravels are more prone to erosion as they have not been
compacted and folded like the rocks that have been pushed up from depths. These young gravels can be found in places like the Omoeroa Saddle just North of Fox glacier.
