When mantle rocks near the earth’s core are heated, they become less dense than the cooler, upper mantle rocks. these warmer rocks rise, while the cooler rocks sink. this movement of warmer and cooler mantle rocks creates pockets of circulation within the mantle which are thought to be the force behind the movement of tectonic plates over the asthenosphere. what method of heat transfer is being described here?

falling water hydro = water .. spectcular places these plants are

here are some information of the future of geothermal energy:

-the future of geothermal energy can pretty much be summed up with a single word: more

-scientists plan in going deeper than 120 meters

-we are hoping that one day, we will get all of our energy from renewable energy sources such as geothermal energy

hope this !

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me

there are no contact forces mentioned on the list of choices that you've provided.