A-off the coast of Mexico. Ocean-continent convergent boundary with volcanoes on the continental side, a deep trench, a Wadati-Benioff zone of increasingly deep earthquakes, and no clear age relation to the boundary. You might find igneous rocks, like andesite or diorite, associated with the volcanoes (as one possible example). You could also talk about deep ocean rocks.
B-African Rift Valley. Divergent, I accepted any crustal type since this is so in transition. We get the formation of new crust, the area is generally low, and we see volcanoes. We also see earthquakes (generally rather shallow). A perfect rock type here might be basalt, since we have a divergent oceanic boundary in parts of this. Different intermediate to mafic volcanic rocks also make sense.
C- Ring of Fire in the Pacific (volcanic chains!)-ocean-ocean convergent boundary. Here, we have another Wadati-Benioff zone of deep earthquakes, abundant volcanoes, a deep trench and then elevated volcanic islands, and no clear age relationship for much of it. Rocks that make sense include ocean floor rocks and intermediate to mafic volcanic or igneous rocks.
What the best answers looked like:
-Standing next to a shield volcano because of diminished hazards and explosivity
-Talked about magma viscosity (tied into mafic and felsic) and how it impacts explosivity for both volcanoes
-Talked about hazards in depth (for stratovolcanoes, ash columns and clouds, lahars, pyroclastic flows, etc.; for shield volcanoes, lava flows, fires, emission of volatiles, some ash, lava fountains). Also gave details (I read a lot about Aa and pahoehoe, and I liked it!) I did deduct points if you put down information that was incorrect.
1. A marine regression has occurred!
2. Since the seashell is buried on the abyssal plain, I would need to dig through shale, then siltstone, then
sandstone to get down to my original layer.
3. Walther's Law states that we cannot find rocks in a vertical sequence that we do not find in environments
that occur next to each other in sedimentary sequences. Our vertical changes should match our horizontal transitions, in other words. This occurs because environments migrate laterally when sea level rises or falls.
4. Going from onshore at the beach to offshore, I would expect to find sand (that would turn into sandstone), then silt (which would turn into siltstone) and then way offshore and on the abyssal plain,shale.
5. In this particular case, at our first time interval we had a sandy beach environment that turned into
sandstone-this is where I buried my shell. After sea level rose, the silty shelf environment that used to be next to the beach but in deeper water would now have migrated on top of the old beach deposits, where the water would now be deep. This would deposit a layer of silty sediment that would turn into siltstone. At an even later time, as water level rose yet higher, we would see the migration of the shale-forming environment on top of our original location. This gives us our sequence of sediment: we dig through shale, then siltstone, then sandstone to retrieve the shell.
Oldest to youngest:
A, B, M, C, D, (L perhaps), E, F, G, H, J,
N, I ( L perhaps), K
Look at this lovely home on this nice, grassy hillside! Unfortunately, all is not well for the inhabitants and they are starting to feel uneasy. What mass movement phenomenon are the trees showing evidence of? (1 point) If we look at the front of the hill, you can see more evidence of mass movement. Assuming that we are looking at earth and dirt that has slid in a cohesive block down this hill, what kind of mass movement is this? (1 point) FINALLY, given unlimited finances and resources as well as access to any kind of equipment that you want, describe three fundamentally different solutions that could be used to make this hillside safer for the inhabitants of this home. You CAN move this house during hillsope engineering, but in and of itself moving the house does NOT count as a solution. You should tell me specifically HOW these mechanisms will work (i.e., will they impact the angle of repose, and how?, etc.) (12 points) (14 points total) Varves, Tree rings, Ice cores, Packrat middens, stable isotopes. One of my favorites - packrat middens - they build garbage middens, and puts material from within a 30-100 meter radius of its midden into it. This gets cemented together with its viscous urine, which forms a substance called "amberat". Middens tend to be tens of thousands of years old (the oldest one dated is over 50,000 years old), may be stratified, and are frequently found in clumps - packrats like to build them under sheltered rocky areas. We use radiocarbon dating on these. The composition of middens tells us about changes in species abundance, and changes in plant communities. Preservation of plant and animal material can be exceptional (some packrats will take dung/skeletal elements from other animals and incorporate them into the midden) 1. Changes in incoming solar insolation
our current sun is warmer than our sun was 4.56 GA
Solar luminosity has increased through time
2. Configuration of continents
Drake Passage is an opening where South America and Antarctica used to be connected
Formed due to spreading and regional tectonics over the last 20-40 million years
This impacted modern circulation by allowing the Antarctic Circumpolar Current to form, which circles Antarctica
This impacted our entire global circulation system and resulted in cooling at high southern latitudes
3. Changes in albedo/reflectivity
Isolation of Antarctica would have impacted its albedo
When we form snow, it reflects incoming solar insolation → drives global cooling
Albedo is highly variable globally
4. Changes in our atmosphere
our atmosphere is varied in composition
Major greenhouse gases are:
Cause warming to the Earth mainly exist in troposphere → closest layer to the Earth
Sun emits solar radiation
Passes through the atmosphere unchecked and hits the surface of the Earth
It may be reflected back into space (especially from surfaces with high albedo) or may be absorbed and re-radiated as infrared radiation
Infrared radiation can then trapped by greenhouse gas molecules
Some infrared heat escapes into space and some gets radiated between molecules
By these actions, greenhouse gases serve as an insulating blanket for Earth → they catch re-radiated heat and warm the surface of the Earth and the lower atmosphere
We need this effect or the Earth would be very cold and would have no liquid water, and possibly life
5. Plate tectonics and weathering
Drop in carbon dioxide when Himalayas formed because weathering caused erosion and created new minerals
Most (non-sedimentary) rocks on the Earth's surface form under high temperature and pressure conditions
When they are exposed to lower temperature and pressure conditions at the Earth's surface, they are no longer stable and break down
These reactions produce new minerals
Water + carbon dioxide = carbonic acid
Carbonic acid + silicate rocks = clays, bicarbonates, and other ions
Animals take the bicarbonates and other ions, make their shells, die, and sink to the seafloor
We can cool global climate by locking up atmospheric carbon dioxide in carbonate rocks, which are made of the skeletons of organisms