Ocean=> 1.03 g/cm^3 (0-3.3 km)
Crust=> 2.7 g/cm^3 (10 km oceanic - 70 km continental)
Upper Mantle=> 3.0 g/cm^3 (90 km oceanic - 130 km continental ~ beneath crust in lithosphere)
Asthenosphere=> 3.3g/cm^3 (250 km thick)
Mesosphere=> 3.6-4.3-5.7g/cm^3 (2500 km thick)
Outer Core=> 9.7-14 g/cm^3 (2250 km thick)
Inner Core=> 14-16 g/cm^3 (1230 km radius)
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According to Abiotic Oil Theory:
(1) Oil is generated at pressures of greater than 30 kilobars in the Earth's Upper Mantle which is located many kilometers below the Oceanic and the Continental Crusts in the lower part of the Lithosphere. It is due to plate tectonic activity such as earthquakes and volcanoes that oil is forced upward some 100 kilometers through the crevices of the upper mantle and the crust until it reaches an impermeable capstone layer where it becomes trapped.
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(2) Oil is often times falsely associated with sedimentary rock because sedimentary rock (organic silts and detritus) tends to accumulate in the same crevices that the oil upwells through. On the oil's migration upward, it tends to pick up fossil remnants, leading people to falsely conclude that the sedimentary rock is actually a source rock. Of course, sedimentary rock does not get compressed into diamondoids as is quite typical of the carbon in the temperatures and pressures of the Earth's crust, and there are many other anomalies that can only truly be explained by abiotic origins of the oil deposits that are being found.
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(3) The following fluid dynamic model is a simulution from an article in New Scientist of magma rising in a volcano through a gradient of varying densities and viscoscities. According to a hypothesis made by Oil_Is_Mastery in his post Rethinking Mantle Plumes, after the main magma bulb fails to rise quickly enough to escape the surface level of the volcano, and thereby causing it to cool and sink back down, the less dense material that continues to rise to the surface is quite possibly oil.
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Sources: See The Earth's Interior & The Thermodynamic Stability of the H-C Systems & Oil Is Mastery &
for more information about Abiotic Oil Theory and Magma Plumes.