[gurpal (OP)]

what does the rock cycle do, how does it work and how does it help humans and other animals?

[MOD EDIT - PLEASE PHRASE YOUR POST TITLES AS QUESTIONS, IN LINE WITH FORUM POLICY, THANKS, CHRIS]

[Bass]

Where to start?  The rock cycle = geology.

The basic idea is that rocks are recycled in the earth's crust and mantle.  Rocks exposed at the surface are subject to mechanical and chemical weathering.  The erosion creates sediments.  Sediments accumulate, are buried and lithify, forming sedimentary rocks.  

Metamorphic rocks are created with the addition of heat and/or pressure.  The original rock constituents change, or metamorphose, to form new minerals and rock.

Adding even more heat and pressure- the rocks melt to form igneous rocks.  Igneous rocks may be erupted on the surface- volcanic- or may cool slowly underground- plutonic.

Igneous/metamorphic zones are uplifted, exposed to erosion, and the cycle begins all over again.

That's a very simplistic view of the classic rock cycle.  

Plate tectonics adds another dimension- new crustal rocks are created at mid-oceanic ridges, accumulate sediments (sedimentary rocks) as they traverse the ocean basins and are consumed at continental edges (subduction zones).  At subduction zones, parts of the basin volcanic/sedimentary package is mashed into the continental edge as ophiolite sequences, and part melts during subduction- creating further igneous and metamorphic rocks, as well as uplift.  Uplifted rocks are subject to erosion, beginning the cycle anew. Again, a very simplistic view of a very complex process.

How does the rock cycle help life?  Without the rock cycle, air, water and surface relief wouldn't exist.  Most of the atmosphere was derived from eons of volcanic activity.  Continents and ocean basins wouldn't exist.  And all the minerals necessary for life, and for human activity, were formed in the rock cycle.

Does life affect the rock cycle?  Absolutely.  Bacteria, fungus, lichen, algae, plants, etc all help with chemical and mechanical weathering.  Algae created atmospheric oxygen, which allowed oxidation and deposition of certain minerals.

Again, this is barely scratching the surface- if you have a more specific question on the rock cycle, the answer can be much more focused.

[JimBob]

Now Bass, you know full well the rock cycle stars with a few kids playing their drums and guitars in a garage, they practice, get a few gigs, are discovered, press a few records, go on tour, become famous, then break up and have a reunion concert 30 years later if one doesn't die of a drug overdose.

That's the rock cycle.