Re: how cold is the bottom of the ocean in the deepest ocean?

Hi Rachel:

Here is a profile of temperature with depth from the Challenger deep, which is the deepest place in the ocean- it's in the Marianas Trench in the Pacific Ocean, near the Phillipines.

As you can see, the temperature is lowest at about 1.5 ^oC at around 3000 metres, and increases to around 2.5 ^oC at the bottom (2.48 ^oC at 10035 m, if you want to be exact). The reason that the temperature starts to increase with depth is because pressure increases with depth (the deeper in the ocean one goes, the more water is pressing down from above). The pressure "squeezes" the water molecules closer together, which increases the number of collisions between molecules, and produces heat.

Hope that helps!
Rob Campbell, MAD Scientist