Plate Tectonics, Earth Interior, Seafloor Bathymetry, and Structural Geology

Comprehensive practice flashcards in fill-in-the-blank style covering continental drift, seafloor spreading, Earth's internal layers, plate boundaries, subduction processes, seafloor bathymetry, and structural geology.

Plate tectonics is often referred to by geologists as "the __________ unifying theory of geology".

grand

The scientist who was the early twentieth-century proponent of the continental drift hypothesis was __________.

Alfred Wegener

Continental drift was not widely accepted at the time because Wegener proposed no viable __________ to explain continental movement.

mechanism

The fossil fern found distributed across South America, Africa, India, Antarctica, and Australia that provided evidence for continental drift was __________.

Glossopteris

The geologist and naval officer who mapped the modern ocean floor, focusing extensively on the Mid-Atlantic Ridge, was __________.

Harry Hess

Dating of oceanic crust reveals that it is __________ at the mid-ocean ridge crest and becomes progressively older away from the ridge.

youngest

Ocean-floor magnetometer surveys documented a symmetrical pattern of normal and __________ magnetic polarities mirrored on opposite sides of mid-ocean ridges.

reversed

The concept of mid-oceanic ridges acting as conveyor belts generating new lithosphere that moves outward in opposite directions is known as __________.

seafloor spreading

Earth's solid inner core is the most dense portion of the planet and is composed primarily of nickel and __________.

iron

The flow of fluid conductive metals within Earth's liquid __________ produces the planetary magnetic field.

outer core

Representing the largest component of Earth's volume, the __________ is solid with local zones of melting and less dense than the core.

mantle

Compared to continental crust, oceanic crust is thinner, denser, and chemically similar to the composition of the underlying __________.

mantle

The boundary marking the physical and chemical change between Earth's crust and the upper mantle is the __________ discontinuity.

Moho

Earth's crust and uppermost mantle are welded together into rigid, brittle segments called plates that comprise the __________.

lithosphere

Lithospheric plates ride directly over top of the partially molten, flowable mantle layer termed the __________.

asthenosphere

The three primary types of tectonic plate boundaries are transform, convergent, and __________.

divergent

Divergent boundaries between two continental plates form narrow, linear valleys known as __________ basins.

rift

When two oceanic plates converge, the plate that is subducted into the mantle is the __________ plate.

older

During continental-continental collision, massive mountain ranges form without subduction because continental crust has too __________ a density to sink.

low

Along transform boundaries, such as the San Andreas Fault, plates grind horizontally past one another, producing numerous __________ earthquakes.

shallow

A continental boundary where continental and oceanic crust are attached and move together in the same direction without subduction is called a __________ margin.

passive

The process where one tectonic plate descends beneath an adjacent plate and sinks into Earth's interior is called __________.

subduction

Oldest continental crust dates to approximately $\sim 4.4\text{ billion}$ years old, whereas the oldest preserved oceanic crust is only approximately $\sim$__________ years old.

$$180\text{ million}$$

Volcanic arcs produced by subduction zones consistently form just __________ of the trench on the overriding plate.

inland

The scientific study that measures and documents seafloor topography and depth zones relative to sea level is called __________.

bathymetry

On a passive margin, the shallow, gently inclined submerged platform underlain by continental crust is the continental __________.

shelf

The relatively steeply inclined boundary zone that marks the transition from the continent to the ocean basin is the continental __________.

slope

Submarine canyons eroded into the continental slope frequently terminate in thick lobes of sediment called __________ fans.

deep-sea

A dense, gravity-driven underwater mixture of water and fine sediment that flows down the continental slope is a __________ current.

turbidity

The continental rise transitions into the true deep ocean floor and is underlain by __________ crust.

oceanic

Because they are far removed from terrestrial landmasses, sediment deposited on abyssal plains is predominantly __________ in origin.

chemical

In structural geology, the force applied per unit area to a rock body is termed __________.

stress

The change in shape, volume, or size of a material resulting from applied tectonic forces is called __________.

strain

The type of stress that causes rock units to slide in opposite directions across a plane is __________ stress.

shear

When deformed rock materials fail to return to their original dimensions once stress is released, their behavior is described as __________.

ductile

On a geologic map, the compass direction of the horizontal line formed by the intersection of an inclined layer with a horizontal surface is called the __________.

strike

The angle of inclination of a tilted rock layer measured downward from horizontal is the dip, which is always oriented at an angle of $\_\_\_\_\_\_\_\_\_\_^\circ$ to the strike.

$$90$$

An arch-shaped fold geometry produced by compression where the oldest rock layers occur along the center of the fold axis is an __________.

anticline

A trough-shaped fold produced by compression in which the youngest strata occupy the central trough is a __________.

syncline

A fold whose hinge line is inclined relative to the horizontal plane, causing the fold axis to dive into the Earth, is a __________ fold.

plunging

In an overturned fold where compressional forces are severe enough to push the axial plane into an essentially horizontal orientation, the fold is termed a __________ fold.

recumbent

A circular, upwarped structural feature where beds dip outward away from a central point and erosion exposes the oldest rocks at the center is a __________.

dome

A circular downwarped structure where rock strata dip inward toward a central point, leaving the youngest rocks exposed in the center, is a structural __________.

basin