Glossary :: S

S Waves

A seismic body wave that has motion perpendicular to the direction of travel (i.e. like light waves). They cannot travel through liquids and are slower than P Waves

Sandstone

A clastic rock composed of sand-sized grains, i.e. between 0.625 and 2mm. The term usually implies a quartz rich composition, although this is not strictly necessary.

Seismology

The study of earthquakes and the structure of the earth via seismic waves. This covers whole earth structure (global seismology) and crustal structure (exploration seismology). Exploration seismology is used in commercial operations, such as oil explorati...More

Sexual selection

Variation in reproductive success due to variation in the ability to acquire mates.

Silica Tetrahedra

All silicate minerals have a structure based on the silica tetrahedra, an arrangement of 1 silica atom and 4 oxygen atoms. The chemical formula for this is SiO4....More

Silicate

A mineral formed from silica and oxygen. The majority of rock forming minerals are silicates. Examples are quartz and pyroxene.

Sillimanite

A polymorph whose other two minerals are kyanite and andalusite.

Silurian

A geological period; the third of the Paleozoic Era from 439 to 409Ma. The fossil record from this period includes a huge variety of marine fossils, land plants and early invertebrate land animals.Epochs:Pr�dol� 411-409Ma Ludlow 423-411Ma Wenlock 430-423M...More

Slickenside

A polished or smooth fault surface. The direction of the last fault movement can be determined by feeling which direction is smoothest with your hand.

Sole Structure

Found in sedimentary rocks, a sole structure or sole mark is a cast found on the base of the rock unit. They are often well developed when a coarse grained rock overlies a fine grained rock. Sole structures can be formed by sticks or stones being carried ...More

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