Glossary - The Solid Earth - page 663

sill small igneous body that has been intruded into and parallel with the existing rock strata.

sinistral fault see left-lateral fault.

solidus surface in pressure-temperature space below which the system is wholly solid.

specific heat amount of heat necessary to raise the temperature of 1 kg of a substance by
1 ◦ C; measured in J kg − l ◦ C − l ; symbol, c P .

strain deformation of a body expressed as change in dimension (e.g., length) divided by
original value of that dimension.

stratigraphy classification of strata in sedimentary rocks.

streamline line marking the position of a particle in a flowing fluid at successive times.

stress force acting on a body, expressed as force per unit area or pressure.

strike-slip fault fault on which the movement is horizontal and parallel to the strike of the
fault; see left-lateral and right-lateral faults.

subduction process by which a lithospheric plate sinks into the mantle.

subduction zone region where one lithospheric plate descends beneath another into the
mantle.

subsidence sinking of part of the surface of the Earth; possible causes include loading and
thermal contraction during cooling.

surface wave seismic wave that travels in the surface layers of the Earth; Love waves and
Rayleigh waves are surface waves. The amplitude of the wave decreases with depth.

surface-wave magnitude magnitude of an earthquake as estimated from measurements of
the amplitude of surface waves.

suspect terrain (terrane) terrane that is suspected of having originated far from its present
location.

S-waves see body waves.

syncline a fold, concave upwards, whose core contains stratigraphically younger rocks.

tectonics geological process that involves the movement of solid rock; the carpentry of the
Earth.

terrain (terrane) geological unit bounded by faults and differing markedly in structure or
stratigraphy from its neighbours; see accreted terrane, suspect terrane.

tesla the unit of magnetic field; one tesla ( 1 T) is equal to 1 kg A − l s − 2 .

thermal expansion change in volume of a sample of material divided by its original volume
for an increase in temperature of 1 ◦ C; units are ◦ C − l , symbol, α .

tholeiitic family name of silica-saturated basalts.

tonalite granitoid rock with quartz together with plagioclase-feldspar, the plagioclase making
up more than 90% of total feldspar.