Odd Earth Objects (L34) Flashcards
What is the story of Lake Nyos?
people died mysterally in their sleep.
an observation made that after the disaster, Lake Nyos developed a strange orange color the day after the event, seemingly without explanation
the volcano occupied by Lake Nyos hasn’t been dormant for at least 400 years
so basically, below the freshwater cap, the bottom water is very salty due to volcanic fluids from the magma champer
below this, large quantities of carbon dioxide has been accumulating for 400 years
it could no longer be contained and escaped into the surface and suffocated victims
What was done after the disaster of Lake Nyos to prevent something like this from happening?
A lake water piping system has since been installed
allows the slow gradual release of co2 from the lake bottom
How are the big boulder rocks in Death Valley actually moving?
in the winter, when water is present of the playa, it freezes at night to form a thin layer of ice
when the ice melts, it creates a thin sheets of water that are moved by wind
the wetting of the mud on the playa surface makes it slick, so that the floating ice sheets can push them across the surface
What is Pareidolia?
the tendency of our brains to incorrectly perceive something observed as an object or pattern or meaning that it doesn’t actually represent
What is a mimetolith?
a natural topographic feature, rock outcrop, rock specimen, mineral specimen, or loose stone with the shape of something else
What are concretions?
bodies of locally cemented sediment
Where are concretions commonly formed?
In marine sediment containing lots of organic matter
what do certain bacterias in the process of eating organic matter produce?
Produces bicarbonate, which becomes concentrated in the water filling the pores of the sediment
What happens when this bicarbonate produced during decay combines with dissolved calcium?
it forms crystals of calcite, which glue the sediment grains together into a hard mass
What is an effect of concretion being hard and tightly cemented with minerals?
Concretions tend to be more resistant to weathering and erosion than their host sedimentary rocks within which they grew
Why do concretions assume some unusual shapes?
Due to local diferences in the rate of carbonate cement percipitation, sediment type, and other factors, concretions can assume some unusual shapes
What is crossbedding?
its a sedimentary structure produced by the migration of bedforms under the influence of a water or wind current travelling in a single direction
How are caves formed?
dissolution of limestone, or sometimes evaporites such as salt or gypsum, is initially focussed along cracks and other planes of weakness
over long periods of time, continued dissolution can produce large underground tunnels through whcih underground streams flow
when the water table drops, the tunnels are drained of water, leaving behind empty, air-filled spaces that we call caves
What are stalactites?
icicle-shaped bodies of travertine formed from percipitation of calcite from dripping water
What is the difference between stalactites adn stalagmites?
Stalactites grow downward adn stalagmites grow upwards
but eventually connect in the middle
