Mountains block passages of rain casting a “shadow” of dryness behind them
Plate Tectonics
is called a Unifying Theory because it explains the locations of most volcanoes & earthquakes, as well as the locations & shapes of continents & the distribution of fossils and mineral resources.
Convergent Zone
Same as “subduction”denser oceanic crust sinks into mantle beneath other plate margin. Sinking plate melts to form magma. Rising magma = volcanoes.
Divergent Zone
rising man-tle plume causes plates to separate, spread. Mid-Atlantic Ridge. Same as rift
Transform Zone
Plates slide past one another. Plate movement = earthquakes (San Andrea Fault)
Post WWII seafloor mapping used
sonar & magnetometers. Seafloor ridges & trenches, coupled with seismic data from earthquakes, and other data helped “close the loop” and explain how it happened.
Alfred Wegener (1915)
suggested the name Pangea for the supercontinent that broke apart to form the present day continents.
Oceanic Crust
More dense than continental crust but thinner. Fe-rich.
Continental Crust
lighter, Qtz-rich, light colored.
Makes up 70% of earths crust
Mafic Composition
silicate mineral or rock that is rich in magnesium and iron. example: Basalts
Felsic Composition
a term used in geology to refer to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium
Continental Rift Zones
A long, narrow fissure in the Earth marking a zone of the lithosphere that has become thinner due to extensional forces associated with plate tectonics.
Cascade Mountains
The small part of the range in British Columbia is referred to as the Canadian Cascades or, locally, as the Cascade Mountains (Mount Renier, Mount St. Helen)
Continental Arc System
Cascade Mountains exist because of an offshore subduction zone.
Island Arc System
is a type of archipelago composed of a chain of volcanoes which alignment is arc-shaped, and which are situated parallel and close to a boundary between two converging tectonic plates.
Western margin
Active margin
Eastern margin
Passive margin
Igneous
solidified from molten rock
Sedimentary
hardened sediments, derived from weathering and erosion of older rocks
Metamorphic
rocks that have changed due to heat and pressure
Intermediate rock
from tall, conical composite volcanoes. Inland from Subduction Zones. Medium-colored, explosive pyroclastic ash eruptions and thick lava flows.
Supervolcano
Erupted from caldera type.
Shield Volcano
a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior’s shield.
Diabase in shallow intrusion, Norcross, GA
Youngest igneous rocks in ga
Crater Lake
After Mt. Mazama magma chamber emptied (7,000 yrs ago), the peak collapsed in on itself, resulting in the caldera, which was filled by rain and snow.
Weathering
Breaking down of rock material.
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Chemical and physical
Erosion
is the down-gradient transport of degraded rock (sand, gravel, clay) by way of streams & rivers to eventual deposition in the ocean.
Bedrock turns into saphrolite
Over time, with Physical and Chemical Weathering, the biotite gneiss becomes the saprolite
Gradient
the drop in feet/mile. Steeper gradient = higher stream energy (velocity) and more vertical erosion of channel (downcutting) and less lateral erosion, leading to “V-shaped” valleys in mountains.
“Youthful” Streams
Mountain stream environment High energy, high oxygen content, low temperature= low biodiversity.
Meandering river
A meander in general is a bend in a sinuous watercourse. A meander is formed when the moving water in a stream erodes the outer banks and widens its valley
Most sedimentary rocks were
deposited in shallow marine conditions
Transitional environments
beaches, tidal flats
Emergent
are stretches along the coast that have been exposed by the sea due to a relative fall in sea levels. This occurs due to either isostacy or eustacy.
Submergent
are stretches along the coast that have been inundated by the sea due to a relative rise in sea levels. This occurs due to either isostacy or eustacy.
Rocky Shore
an intertidal area of seacoasts where solid rock predominates.
Sandy Shore
also called beaches, are coastal shorelines where sand accumulates.
East shore
Emergent shoreline. Sandy shore habitat
West Shore
Submergent, rocky shore habitat
Shales
found in deeper and/or quieter water where shales are deposited
Aquatic ecosystem
ecosystems largely controlled by water depth, water energy, clarity.
Symbiotic
close and often long-term interaction between different biological species.
Mutualistic
is the way two organisms biologically interact where each individual derives a fitness benefit.
