GEOLOGY

Detailed explanation-1: -Which phrase describes a sill? Explanation: Sills are horizontal layers in the soil that form as a result of magma. Also, sills are considered sheet intrusion because the hardened magma gets into older rock layers or soil layers and cuts the rocks horizontally.

Detailed explanation-2: -sill, also called sheet, flat intrusion of igneous rock that forms between preexisting layers of rock. Sills occur in parallel to the bedding of the other rocks that enclose them, and, though they may have vertical to horizontal orientations, nearly horizontal sills are the most common.

Detailed explanation-3: -Sills are magma-filled fractures concordant with the layers and bedding of the host rock. Therefore, in young sedimentary basins or active volcanic areas sills are subhorizontal or gently dipping.

Detailed explanation-4: -A volcanic sill is a planar sheet of magma which is parallel to the surrounding rock. Sills store magma compared to dikes which transport magma. The Basement Sill in Antarctica is 350 m thick and 100 km long.

Detailed explanation-5: -Sills can form from magma with a range of silica contents. A renowned example of the sill is the tabular mass of quartz trachyte found near the summit of Engineer Mountain near Silverton, Colorado.