13. Which statement below best characterizes the thermohaline circulation model?

Question

13. Which statement below best characterizes the thermohaline circulation model? a. Cold fresh water from the poles flows on the surface to the equator b. Salty water at the equator cools on the surface and sinks vertically to the ocean floor c. An influx of fresh water into the oceans could increase the circulation d. Water temperature and density differences drive the circulation model 14. If the overburden density is 2200 kg/m' estimate the effective stress at 3.5 km depth? a. 75.46 MPa b. 41.16 MPa c. 10.94 Kips d. 34.3 MPa 15. The half-life for the decay of the Uranium (U)z isotope to the Lead (Pb)zos isotope is 4.5 x 10 years. Mass spectrometer data for a basaltic lava sample indicates that the sample contains 90% (U)238 and 10% (Pb)20. How old is the basalt? N«Noekt a. 4.5 x 10 years b. 5.40 x 10 years c. 2.63 x 10 years d. 6.84 x 10 years 16. Differentiation refers to the process in which the earth: a. accreted from smaller terrestrial bodies b. was bombarded by frequent meteorite collisions c. became chemically segregated due to melting and sinking of iron d. became a separate and distinct planetary body along with the other terrestrial 17. Why isn't the earth's surface dominated by craters like large areas on the Moon's surface? a. The moon's gravity deflects objects away from the earth b. The moon formed much earlier than the earth and was exposed to impacts longer c. The surface of the earth changes over time due to plate tectonics and erosion d. None of the above 18. According to current estimates, the earth's internal temperature is: a. at the melting point in the outer core b. above the melting point in the outer core c. below the melting point in the outer core d. lower in the outer core than in the mantle

Explanation / Answer

13) D.  Thermohaline circulation, also called Global Ocean Conveyor or Great Ocean Conveyor Belt, the component of general oceanic circulation controlled by horizontal differences in temperature and salinity.

14)

ffective stress - pgh

where p - 2200kg/m3 ( density)

g - 9.8 m/s2 ( acceleration due to gravity)

Depth = 3.5 Km ( 3.5 * 1000 m)

stress = pgh= 2200 *9.8*3500 = 75460*103 pascal= 75.460 mpa

15) D

half life of uranium , T1/2 = 4.5 *109

formula for half life and decay constant . T1/2= ln/k = 0.693/4.5*109 = .154*10-9

N =Noe-KT --- 90No= 100No e.154*10to the power -9 == so Time = 6.84 *108 years

N- parent present at time T

No- parent initial

K - decay constant

T - time taken to decay

16) C   The Earth’s differentiation describes its formation into layers, which include its iron-rich solid inner core, its molten outer core, its solid mantle and its crust on which we live.

17) C . earth is dynamic body with its plate motion going continously from the geolical time where new plates are created and older being subducted . hence no visible craters seen on earth.

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