The Origin and Evolution of the Marine Environment (MSCI 112) - Tectonics & Deformation Vocabulary Flashcards

Vocabulary flashcards covering key terms related to tectonics, deformation, rocks, faults, folds, and orogeny from the lecture notes.

Force

An interaction that tends to change the motion of an object; measured in Newtons (N); includes compression, tension, shear, and confining.

Stress

Force per unit area experienced by a rock (N/m^2).

Strain

The amount of deformation resulting from applied stress; includes shortening, stretching, and shear.

Brittle deformation

Deformation that results in fracturing rather than flow; common at lower temperature/pressure or high strain rate.

Ductile deformation

Deformation that involves flow or bending of rocks; common at higher temperature/pressure or slower strain rates.

Confining stress

Uniform pressure acting on rocks from all directions.

Compression

Stress that squeezes rocks together.

Tension

Stress that pulls rocks apart.

Shear

Stress that causes sliding of rocks past one another.

Strike

The compass direction of a rock layer as it intersects a horizontal surface.

Dip

Direction in which a rock layer tilts; measured perpendicular to strike.

Dip angle

Amount of tilting of the layer; measured at right angles to dip direction.

Joints

Brittle fractures in rock surfaces with no movement on either side.

Veins

Mineral-filled cracks formed by fracturing.

Fault

Fracture in rocks along which there is movement.

Normal fault

Fault with the hanging wall moving downward relative to the footwall; caused by tensional stress.

Reverse fault

Fault with the hanging wall moving upward relative to the footwall; caused by compressional stress.

Strike-slip fault

Fault with horizontal motion parallel to the strike; includes left-lateral and right-lateral types.

Fault surface

The planar surface along which a fault occurs.

Fault throw

Vertical displacement across a fault.

Footwall

The rock block below the fault surface.

Hanging wall

The rock block above the fault surface.

Left-lateral strike-slip

The left-hand side block moves backward relative to an observer standing on the fault.

Right-lateral strike-slip

The right-hand side block moves backward relative to an observer standing on the fault.

Divergent boundary

Plate boundary where plates move apart; associated with tensional stress and normal faults.

Convergent boundary

Plate boundary where plates move toward each other; associated with compressional stress and reverse/thrust faults.

Transform boundary

Plate boundary where plates slide past one another; associated with shear stress and strike-slip faults.

Tensile stress

Stress that stretches rocks, pulling them apart.

Compressional stress

Stress that squeezes rocks together.

Shear stress

Stress that causes sliding parallel to a plane.

Folds

Bends or curves in originally flat rocks; results from ductile deformation.

Axial plane

Plane that divides a fold into two roughly symmetrical halves.

Fold axis (hinge)

Line where the axial plane intersects the fold surface.

Limbs

The two halves of a fold separated by the axial plane.

Anticline

A fold with limbs dipping away from the axial plane; oldest rocks at the center/top.

Syncline

A fold with limbs dipping toward the axial plane; youngest rocks in the center; oldest at outside edges.

Plunging fold

A fold whose axis is not horizontal; the fold axis dips into the subsurface.

Monocline

A fold with one limb horizontal; often associated with a blind fault.

Domes

Folds that are circular to oval and stack rocks older toward the center; anticlines in multiple directions.

Basins

Folds that are circular to oval and stack rocks younger toward the center; synclines in multiple directions.

Orogeny

The processes by which mountain ranges are formed through tectonic deformation.

Collision

Convergent tectonics where two plates collide, causing crustal shortening and fold-thrust belts.

Subduction

Convergent tectonics where one plate sinks beneath another; causes crustal shortening and volcanism.

Continental rifting

Tensional tectonics that rift continental lithosphere apart, often forming normal faults and basins.

Exotic terrane

A young, buoyant piece of oceanic lithosphere that does not subduct and accretes to a continent.

Suture

The boundary where an accreted terrane attaches to a continent.

Accretion

Process of adding crustal material to a continent via collision and suturing.

Isostasy

Gravitational balance between crust and mantle; causes uplift or subsidence as loads change.

Delamination

Removal of lithospheric material from below, often leading to isostatic rebound.

Exhumation

Process of rocks being brought to the surface by erosion and uplift.