Tectonics and Climate Readings Flashcards
Montgomery and Willet Date ?
2001
What was Montgomery and Willet paper about?
The significance of exogenic processes in the Andes
Influence of tectonics on Andes?
Uplift of the Andes began 60 million years ago during late Pleistocene
Continuous uplift driven by collision of the Nazca and South American Plates
Create ‘topographic template’
Climate influence on geomorphology of the Andes
more current influences of climatic processes -
due to the Andes longitudinal span runs through range of climatic zones result in differences across the mountainous landscape
1) normal fluvial erosion in Northern Andes = high precipitation = narrow mountain range
2) glacial land sculpting = At higher latitudes glaciers preferentially erode the highest ground in the Southern Andes = excess elevation at the glacial limit and systematic decline in max elevation towards pole
Where is tectonics most dominant in the Andes - and why?
In central Andes
there is little erosion in except in big river valleys
= leads to crustal thickening by tectonic wedge propagation
Creates linear Hypsometry
Quote from Willet and Montgomery
We view tectonics and erosion as a coupled system with potential for feedback between climate driven erosion and tectonic forcing
Raymo and Ruddiman date?
1992
Raymo and Ruddiman - about
Uplift of the Tibetan plateau may have caused global cooling in the Cenozoic led the growth of large continental ice sheets in both hemispheres
Tibetan Plateaux description
elevation exceeds 4500m
surrounded by high mountain ranges - Himilayas to the South
Southwestern China
Largest area of uplifted crust on earth
how did Tibetan Plateau impact in Cenozoic?
Uplift resulted in perturbation of atmospheric circulation on a hemispheric scale
and altered weathering patterns this then resulted in a positive feedback mechanism as glacial erosion further increases erosion and cooling worldwide
Chemical weathering = Increase in drawdown of Co2 = further cooling
General Argument supporting Raymo and Ruddiman
That Tectonic processes can impact effect climate changes resulting in changes to global geomorphic landscape (Work in positive feedback cycles)
Hilton and West - Date
2020
Hilton and West (2020) -
Discusses the ways that mountain building processes effect the carbon cycle
How does silicate weathering effect the carbon cycle?
Silicate minerals, eg.olivine, react with CO₂ and water through chemical weathering.
= reaction removes CO₂ from the atmosphere and converts it into bicarbonate ions (HCO₃⁻) in solution. these are then carried to rivers = to oceans sink
Climate silicate weathering strongest in areas that have highest erosion
Relationship between erosion rate and co2 flux
Where erosion rates are low - weathering products accumulate and shield underlying rocks = weathering limited by supply as material not exposed for weathering
when erosion rates are high - surface area of rock exposed = higher removal of atmospheric Co2 = erosion limited by other factors eg, temperature, Co2 conc
Why do mountainous areas vary in their sink/source relationship to the carbon cycle?
Different mountains underlain by different geology
Sedimentary rocks = carbon rich= carbon source
volcanic rocks = not carbon rich = carbon sink
Molnar et al - date
2007
Molnar et al (2007) -
tectonic fracturing of rock can result in an increased rate of erosion
How does fractured rock increase erosion rate?
reduced rock strength = lower resistance to erosion
broadens the surface area available to erode
disintegration = breaks up into smaller blocks that are easier to transport
Evidence demonstrating the significance of fracturing as an endogenic erosive process-
places where tectonic activity lies dormant rapid erosion does not occur despite high rainfall
Brain - date?
2010
Brain (2010)
new evidence suggests that earths topography is actually cased by viscous stresses from flow in the underlying mantle not just plate movement
Impact of mantle movement on topography -
upward mantle flow = positive topography = high relief
Downward mantle flow = = negative topography depressions
Height of topography = direct proportion to intensity and depth of mantle flow
driven by gravitational force
Where can we study effects of mantle flow? and why?
Australia
Has been tectonically stable since separation from Antarctica
can study how mantle dynamics effect shoreline and surface features
Drowned Reefs in North eastern Australia = resulted due to subsidence during Miocene as result of mantle flow from Subduction north of Papa New Guinea
BLAG Hypothysis - who
Berner et al (1983)
what is Blag hypothesis
Co2 governs the global climate and weathering of silicate rocks
Higher Co2 = increased rainfall = greater chemical weathering potential = removes co2 from atmosphere
Inversely - loss tectonic activity - less co2 release - less weathering = colder climate - icehouse system
Dissolution reaction
calcite + co2 + water —> calcium + bicarbonates
What type of landscapes illustrate the interplay of tectonics and climate acting over a range of spatial and temporal scales?
Karst landscapes
Eg - Dolines
What are Dolines?
natural enclosed depression in karst landscapes
range from metres to tens of meteres in both diameter and depth
Found in - kentucky, Namibia, Temperate UK
exogenic
formed or occurring on the surface of the earth
endogenic
formed or occurring internally, geology. formed or occurring within the earth.
weathering
physical or chemical breakdown of rocks and soil in place
erosion
The process of transporting weathered rock and soil away from where it was broken down.
erosivity
potential of the erosive force
erodibility
resistance of the material being eroded
Denudation
denudation is the sum of all processes that lower the Earth’s surface
exogenic factors that influence weathering
Climate
Vegetation
topography
soil composition
biological activity
Endogenic factors that effect weathering
mineral composition
structural features - eg fractures and faults
geological age
tectonic activity
key drivers of exogenic processes -
Solar energy - atmospheric and oceanic circulation, influencing weather patterns and temperatures, which affect weathering and erosion.
Gravity - mass movements
water - rainfall rivers and glacier
Wind - aeolian erosion
key drivers of endogenic processes -
- Heat from earths interior - Geothermal heat drives processes like mantle convection,
- Radioactive decay - decay of radioactive isotopes generates hear contributes to thermal dynamics
- Movement of tectonic plates
Pressure - due to overlaying rock layers can lead to metamorphism and formation of new minerals
Time scales of exogenic and endogenic processes
Exogenic often much shorter but both can operate at range
