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.
Convection currents is similar to convection of heat (hot air rises, cold air falls and replaces hot air etc). The movement of these convection current in the earth's core and â¦ liquid mantle, causes the earth's crust to move...causing earthquakes etc. 7 people found this useful.onvection currents in the magma drive plate tectonics. Heat generated from the radioactive decay of elements deep in the interior of the Earth creates magma (molten rock) in â¦ the aesthenosphere. 6 people found this useful.