Midterm 1 review Flashcards
what extinction event are we in?
holocene
effect of underwater volcano
worldwide
climate change means what for extreme events?
they become a lot more common because of human contribution
brief cover of scientific method
observation
hypothesis (must be testable & reproducible)
test hypothesis
form theory
geology as a science evolution
first observational but now analytical
how old is earth?
4-5 bya
tilt of earth
23.5
chemical makeup of planets in solar system
4 rocky and metallic inner planets (nearest the sun) then 4 gaseous outer planets (very cold)
how old is universe?
14 bya
origins of planets
young star condense and materials around it condense too (gaseous condense at low temp so outside planets are gaseous and low density while inner planets are solid and mineral- high density)
differentiation of earth
central core: dense and hot (Ni & Fe)
mantle (thick zone around core - ultra mafic and mafic rocks/magma)
crust : (oceanic - mafic and crustal -felsic)
hydrosphere (def.)
all water at or near the surface of the earth
stream (def.)
body of flowing water
river (def.)
major branches of stream system
drainage basin (def.)
where the stream gets its water supply
what does the size of the drainage basin upstream indicate?
the size of the stream
how is the drainage basin defined topographically?
divides
stream discharge (def.)
volume of water that passes point in a given time (m3/s) = area x velocity of flow
laminar flow vs turbulent
parellel streamlines (slow moving rivers or edges of fast rivers) vs mixing streamlines making eddies (fast moving riversO
total sediment load (or just load) carried by a stream = _____. ability to carry material of certain size = ______
-capacity (closely related to discharge and availability of sediment) = increasing v = increase capacity
-competence
slow moving water carries what size of sediment? faster?
-fine-grained
-wider range
stream flow changes with ____ and sediments are well sorted by _____
-seasons
-size and density
when stream profile is stable it is a ___ stream
graded
velocity of stream is largely dependent on steepness of channel = ____
gradient
base level of stream = _____
lowest elevation stream can flow, typically sea level if linking to sea (gradient decreases as you get closer to base = longitudinal profile); can be lake, dry alley
two types of stream types
meandering: gentle gradients, cary fine sediments
braided: diverging, steep gradients and high sediment load & changes in discharge
forming meandering stream
low-velocity stream in flat floodplain
-sediment deposited when water is bending (inside banks) & current slower = point bar
-snajing motion
meandering stream eventually forms _____
floodplain
hydrograph (def.)
a plot of stream discharge at a point over time (ex. base at jan , feb, mar)
factors governing flooding
-excessive rainfall
-snowmelt off in mountains
-severe storms
-hazardous blockage of stream channel (tree & rock avalanches)
-any time input exceeds output
_______ of stream increases during flood
-velocity , height and discharge
stage (def.) crest (def,)
-elevation of water (flood tage: stream exceeds bank height)
-crest (max stage reached)
upstream flood (def.)
happens in small localized upper part of basin, usually internse rainstroms or dam bursts
downstream flood (def.)
happens in large lower part of drainage basin, heavy rains/snow melts , last longer in duration
flash flood (def.)
type of upstream flood characterized by rapid rise in stream stage (usually by thunderstorm)
ice jam (def.)
ice doesn’t melt properly, ice stucks together, can constrict flow and cause flood
stream hydrographs + flooding
upstream: smaller drainage basin = steep increase in discharge, short duration
downstream: drainage basin larger, smaller peak in discharge, water is spaced out so broader peak of longer duration
rate of surface runoff influenced by (4)
ground cover
topography
presence of vegatation (increase inflitration)
climate
flood frequency curve
-Useful tool to evaluate frequency of flood events
- Curve is constructed by plotting discharge as a
function of recurrence interval
building a dam vs urban growth effect on flood
building dam=decrease flood risk
urban growth = increase flood risk
Flood Hazard Reduction Strategies
- Restrictive Zoning
- Retention Pond
- Diversion Channel
- Channelization (straighten channel - reduce local damage but increase downstream)
- Levees
- Flood Control Dams and Reservoirs
don’t build in flood plain
major mass extinctions + when they occured? + volcanism
Silurian-Ordovician - 450 Ma
Late Devonian - 320 Ma - Viluy Trap
Permain -Triassic (largest) - 252 Ma -Siberian
Triassic -Jurassic 200 Ma -CAMP
End Cretaceous (K-P)- 66Ma- Deccan
Permian extinction effects
-marine invertebrates suffered (especially those with CaCO3 exoskeletons) - corals, ammonoids, trilobites lost
-terrestrial invertebrates = largest extinction of insects
-terrestial vertbrates = large herbivores suffered
terrestial plants - loss of forest (coal gap)
Earliest Triassic shallow marine settings are
characterized by ______
-very few fossils and few trace fossils.
* High diversity assemblages occur in isolated refugia
paleozoic coral types went extinct at aend of permian = new coral type
scleractinain coral appear in middle triassic
Triassic-Jurassic extinction event
collapse of reef, ceratitic ammonoids
mammals largely unaffected
Triassic-Jurassic extinction event cause
CAMP (central Atlantic) originc of mid atlanic rift = northamerian africa, south america
Cretaceous-Paleogene Extinction Event
most of planet and animals, not tetrapod over 25 kg surviveved, demise of non-avian dinosaurs.ptersours,
chicxculb impact
65 mya
mexico, created tsunami,
evidence: shocked quartz, glassy spheres,iridium at K-Pg boundary
also tanis site
C-P extinction = ____ volcanism
decaan trap (india)
brief history of mammals
1st mammal in triassix
marsupial in early cret.
placental in paleogene
primate in early paleogene
what did Grabau work indicate?
the crust indicated that sea level rised and fell rhythmically
other scientists involved with flooding?
barrell, sloss (indicated that there were 5 times in earth history were covered with water)
glacation effect on sea level
sea level decrease
glacial melting effect on sea level
sea level increase
gradualism/uniformitarianism
we used to believe that crust changes happen gradually
what indicates that gradualism wasn’t true?
1)omission of geological time between layers
2)sedimentary deposits that are weird
3) fossil rich levels (aka bone beds)
Catastrophism
features from large abrupt changes
Catastrophic Uniformitarianism
both slow and rapid process shape Earth
flood (def.)
overflow of water on land that is usually dry; cause: tsunamis, rapid melting with volcanism)
mythical origin of Mediterranean
hercules dug an inlet between africa and rock of gibraltar
what was messinian salinity crisis
The Mediterranean Sea became disconnected from the world’s oceans and mostly desiccated by evaporation about 5.6 million years ago during the Messinian salinity crisis
what was zanclean flood?
The Atlantic waters found a way through the present Gibraltar Strait and rapidly refilled the Mediterranean 5.33 million years ago in an event known as the Zanclean flood. (0.4 m per day to 10 m) (western basin filled first then eastern)
Sea-level Changes last 20Ka
A: The flooding of Doggerland: The coastline
around the North Sea centered on the Dogger
Bank, at 10,000 BP and 7000 BP, after Shennan
et al. (2000), with permission.
B: The flooding of Sundaland: The coastline
around the Sunda Shelf at 11,560 BP and 7240
BP, from Sathiamurthy and Voris (2006).
C: The flooding of Beringia: The coastline
around the Bering Strait at 12,000 BP and 7000
BP.
hurricanes, cyclones, typhoons
same type of storm called different things; warm air in middle (lowpressure)
increasing temp and strength of storm
increasing strength
- Factors that impact coastlines:
– Tectonic setting
– Materials present at the shore
– Energy of water striking the coast
coastlines: Active margin? Passive margin?
- associated with active plate tectonics (Often cliffs found near active margins)
-far from active plate tectonics (Often a broad shelf, beaches and with sandy offshore beaches)
- Signs of changing relative sea level
- A wave-cut platform will form at coastlines: A number of wave cut platforms is an indication of uplifting land or dropping sea level
– A drowned valley can record changes in sea level also
Waves and currents are the primary forces regulating natural _______
Shoreline modification
Waves are induced by winds. While the waves themselves propagate, the water involved actually moves in a circular motion in place. The radius of the circular motion becomes smaller with depth, and is negligible at ____. As waves approach the shore, circular motion is no longer possible and waves collapse, yielding ____.
- the wave base
-breakers
energy of wave?
2^x (x= height)
Tides moving near shorelines cause currents that can reach speeds of a few kilometers an hour. As the tide rises, the water flows in towards shore as a flood tide, moving into coastal marshes and up small streams. As the tide passes the high stage and starts to fall, the ebb tide moves out, and low-lying coastal areas are exposed again.
The area that is exposed is called the _____
-“tidal flat”
Disruption of the longshore current leads to both
unwanted erosion and deposition
Groin Prevents up-drift erosion
BUT… causes down-drift erosion
