Tax returns and supporting documentation. The IRS has three years to challenge your tax returns, so you must keep them at least that long. It's wise to keep tax returns for at least six years, because if the IRS suspects you may have under-reported income, it has six years to challenge returns.
How is the Earth's crust related to tectonic movement? The convection currents in tectonic plates occur in the geosphere. The radioactive decay of elements is responsible for the heat deep within the earth, and this results in the creation of magma. Magma is a type of material that can be semi-fluid or completely fluid.
plate tectonics The roles that convection currents and other forces play in the movement of Earth's tectonic plates. Â© MinuteEarth The process of plate tectonics may be driven by convection in Earthâs mantle, the pull of heavy old pieces of crust into the mantle, or some combination of both.