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.
The movement of the plates is caused by the convection currents of heat from the Earth's interior. This heat, rising toward the surface through the mantle causes movement of plastic like rock in the asthenosphere, the layer of Earth directly below the lithosphere.he Earth's plates are riding on top of the currents caused by these processes. The main features of plate tectonics are: 1  The Earth's surface is covered by a series of crustal plates. 2  The plates are composed of crustal rock and solid upper mantle which is called the lithosphere.