Principles of geomorphology Flashcards
What does the Hjulstrom curve describe?
Erosion thresholds based on particle type and velocity (force and resistance)
What does the Hjulstrom curve describe?
Erosion thresholds based on particle type and velocity (force and resistance)
What are the 5 key principles of geomorphology?
EFTFT
1. Equilibrium
2. Force (and resistance)
3. Thresholds
4. Feedback
5. Time
Describe uniformitarianism
Geo formation processes are slow and steady over time – this helps us understand the history & nature of landforms
Describe catastrophism
Some things happen very quickly and dramatically, disrupting uniform patterns in landform evolutions
Describe the general geographic cycle
young -> mature -> old -> young
Give an example of an endogenic process?
Plate tectonics, landform evolution
Give an example of an exogenic process
Weathering, erosion, transport, deposition
What is a morphological system?
A system where the morphology is influenced by forces acting upon it
forces affect morphology - morphology affects further morphology
What is a cascading system?
The output from one system becomes the input for another. Dynamic system characterized by transfers in mass and energy
What is a process-response system?
system that integrates characteristics of morphological and cascading systems
What are the 4 types of equilibria?
-Static
-steady-state
-dynamic
-Dynamic-metastable
Energy: What are the key sources of energy in the geomorphological systems?
-Solar system: rotational energy
-Solar radiation
-Gravitational attraction
-Plate movement
-Geothermal heat flow
What are the 5 contributing factors of landscape evolution?
-Climate
-Tectonics
-Topography
-Geology
-Biology
How does an igneous rock form?
Directly from the cooling, solidification & crystallization of magma
ex. basalt, granite
How does a sedimentary rock form?
From the compaction and cementation (lithification) of erodied and deposited sediments.
Key processes: weathering, erosion, transportation, deposition.
ex: sandstone, limestone, shale.
How are metamorphic rocks formed?
When any igneous or sedimentary rock undergoes physical or chemical changes under pressure & increased temperature. They are usually buried.
The metamorphic changes in mineral type always reflect the restoration of equilirbium
ex: slate, gneiss, marble
What are the parts of the earth’s structure (spheres)
Lithosphere - outer
Asthenosphere - middle
Mesosphere - inner
Describe the continental crust:
-general composition
-avg density
-avg depth
-upper composition
-lower composition
-General composition: SiAl (silica & aluminum)
-Avg density: 2.7g/cm3
-Avg depth: 30-40km
-Upper composition: granite rocks
-Lower composition: basalt and diorite
Describe the oceanic crust:
-general composition
-avg density
-avg depth
-general composition
-General composition: SiMa (silica & magnesium)
-Avg density: 3.0g/cm3
-Avg depth: 6-11km
-Composition: Tholeiitic basalt
What are the 3 sources of knowledge to understand earth’s inner structure?
Volcanoes
Gravity measurements, magnetism
Seismology - earthquakes
What did the geophysicist Inge Lehmann discover?
The existence of the inner core via extra vibrations coming from what must have been the inner core
What is isostasy?
adjustment of the earth’s crust in response to something weighing on the lithosphere.
Continental drift: when did Pangea, the supercontinent, exist?
200-250 mya
What lines of evidence are there for Pangea?
-Fossil similarities across several regions (particularly Gondwanaland)
-Patterns of glacial erosion, deposits & geology
What 4 scientific developments spurred the plate-tectonics theory?
-Demonstration of ruggedness and youth of the ocean floor
-confirmation of repeated reversals of the Earth magnetic field in the geologic past
-Emergence of the seafloor-spreading hypothesis + associated recycling of the oceanic crust
-Precise documentation that the world’s earthquake & volcanic activity is concentrated along oceanic trenches & submarine mountain ranges
Seafloor spreading
What are the 3 types of results of crustal movement / uplift?
-tectonic mountains
-volcanic landforms
-residual mountains (remnants of ancient tectonic activity)
What are the 3 types of plate boundaries?
-Divergent
-Convergent
-Transform fault (sliding past each other)
What are the 3 types of convergent boundaries?
-subduction
-convergent
-transform fault margins
What is epeirogeny?
change in the global disposition of land masses (e.g. continent formation)
What is orogenesis?
Process of mountain formation driven by plate tectonic movements.
What is diastrophism?
The combination of epeirogeny and orogenesis - folding or faulting
What are the 2 forms that a diastrophic fold can take ?
Anticline & Syncline
What are the 3 types of plate boundaries?
Divergent
Convergent
Transform Fault (sliding past each other)
What type of movement is the seafloor spreading cycle?
Convectional
What causes seafloor magnetic stripes?
volcanic flows that cool during different orientations of earth’s magnetic pole
What is regolith?
an unconsolidated surface layer of weathered rocks
Why do rocks weather?
rocks exposed at the surface
by erosion are no longer in
equilibrium with their environment
What are the 4 types of physical weathering?
-Freeze/thaw (frost action)
-Exfoliation (expansion/contraction)
-Abrasion
-Root wedging
How does chemical weathering affect physical weathering?
Chem. weathering creates more stable, but more breakable, chemical compositions. They become physically weaker.
How does physical weathering affect chemical weathering?
Physical weathering increases the surface area for chemical weathering to take place.
