part one Flashcards
uniformitarianism
the idea that geomorphic processes are a result of laws that are uniform through time and space therefore we can look into past to understand landscape evolution and interpret earth history
when was uniformitarianism first proposed and by who
in 18th cent in response to catastrophism by hutton and popularised by lyell
what has the inital uniformitatrian
the uniformity of processes rates and states and landscapes (no dynamic variability, unpredicitatedn events and catastrophies)
what are the two types of uniformintarnisms
- metholodical (different rates of chnage and non linear events however uniform laws - by GOULD 1965)
- substantive (lyell and hutton steady rates overtime)
describe geomorphic systems thinking
a system is limited by a boundary comprising of internal components and processes that create outputs and inputs of enegery
why do we see the same landscapes and patterns repeatted
equilibium theory. balance of competing forces. a normal state for a geomorphic system
what is base level
the lowest altitude at which erosion can occur (sea level or local base eg dam)
rejuvination
regarding of river profile in reponse to change in base level
what is dynamic equilivium
constant rebalancing in reponse to exogenous forces
what is meta stable equilibrium
more than one equilibium state defined by thresholds and history
what is the cyclical model of earth surface
by william davis
planation and denudation. all systems wear down
what us denudation
wearing of earrths through erosion
what is planation
denudation pathways to base level
peneplain
large continuous low releif area to base level
pediplanation
denundation through scarp retreat and slopes remain
what is a critical zone
area of focus, air to ground water all processes reponsible for converting bedrock to soil
how is the climate a major exogeneous control
temp and precipitation: control of weathering on system. (denudation rates)
shallow soils in dry cold regions vs deep soils in humid wet areas
what are 3 characteristsic of the creatceous climate
high hates of co2, global mean temp 10 degrees more
strong hydrological cycles
high sea levels (no ice caps) ~200 m higher
when was the createous
100 million years
evidence of createous climate
stomata based fossils (less frequent and smaller stomata due to excess co2)
how has the temperature gradient different fro createous vs now
createous was less extreme, mean average at poles14 degrees. today with ice at caps there is more of a gradient due to albedo effect
what caused high co2
degassing of rock reservoir due to high tectonic activity, and super plumes. production exceeded rate of sequestration
what caused high sea levels
Bathymetry: rapid production of new ocean crust pushed up water due to higher elevation (less dense),
lack of ice caps
thermal expansion
more hydological cycle
what caused the progressive cooling
slowing of mantle convection reduced seafloor spreading, concumption of co2 by chemcial weathering (more sequestration), aging of oceanic crust and permanent ice albedo
