What is the volumetric rate of oceanic crustal production, given a typical seafloor spreading rate of 9.8 cm/yr (full rate), oceanic crustal thickness of 7.0 km, and a length for the global mid-ocean ridge system of 60,000 km? Please give your answer in units of km/yr. 1 m = 102 cm, 1 km = 103 m. B. Given that the Earth is not changing in size, what must be the global rate of crustal subduction? C. Assume that the ocean crust is 5% porosity by volume. What the global rate of subduction of seawater? Please give your answer in units of km/yr. D. Seawater is 35 part per thousand dissolved salt, about 36.4 kg/m3. What is the global rate of dissolved salt subduction by seawater in the ocean crust? Please give your answer in units of kg/yr. 1 km= 109 m. 58. Define these terms: ice age, glacial, and interglacial. Be sure to (a) list the timescales over which each of these occur, and (b) describe which of these terms apply to Earth’s current climate.

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