Geology: Tectonic Plates, Stress, and Rock Dating

Vocabulary flashcards covering tectonic plates, plate boundaries, geological stress, rock layer formation, relative dating principles, and absolute dating.

Tectonic Plates

Large pieces or segments of Earth's rigid outer layer called the lithosphere that are in constant motion.

Lithosphere

Earth's rigid outer layer that is divided into tectonic plates.

Asthenosphere

The layer beneath the tectonic plates where heat from Earth's core causes currents that help move the plates.

Continental Drift Theory

The theory proposed by Alfred Wegener in 1912 stating that all continents were once joined as one supercontinent called Pangaea.

Alfred Wegener

The scientist who proposed the Continental Drift Theory in 1912.

Pangaea

The ancient supercontinent that joined all Earth's continents together before they drifted apart.

Continental Plate

A type of tectonic plate that forms continents; it is thicker and less dense than an oceanic plate.

Oceanic Plate

A type of tectonic plate that forms the ocean floor; it is thinner and denser than a continental plate.

Convergent Boundary

A plate boundary where tectonic plates move toward each other, capable of causing mountains, volcanic activity, and earthquakes.

Divergent Boundary

A plate boundary where tectonic plates move away from each other.

Transform Boundary

A plate boundary where tectonic plates slide past each other horizontally, causing earthquakes as they grind together.

Rift Valley

A geological feature formed at a divergent boundary between two continental plates.

Volcanic Island Arcs

Geological structures formed at a convergent boundary where two oceanic plates meet and the denser plate dives under the other.

Oceanic Ridge

An underwater feature formed at a divergent boundary between two oceanic plates where new seafloor is created.

Stress

A force acting on rock that changes its shape or volume.

Tension

A type of stress that pulls the crust apart, stretching and thinning the rock.

Compression

A type of stress that squeezes rocks, causing them to fold or break.

Shearing

A type of stress that pushes rock in opposite directions.

Sediments

Materials such as gravel, sand, and mud formed when older rocks are broken down by water or wind.

Relative Dating

A method used to determine which rock or event is older or younger without giving an actual numerical age.

Absolute Dating

A method used to determine the exact numerical age of rocks using radioactive decay.

Law of Superposition

A relative dating principle stating that in layered sedimentary rocks, the top layer is younger than the bottom layer.

Law of Original Horizontality

A relative dating principle stating that rock layers are originally deposited horizontally, and tilted layers result from later events such as mountain building.

Law of Lateral Continuity

A relative dating principle stating that rock layers originally extend sideways/laterally, allowing matching layers to be identified even if erosion removed parts.

Law of Cross-Cutting Relationship

A relative dating principle stating that a fault or igneous feature that cuts through another rock is younger than the rock it cuts.

Radioactive Decay

The process where a radioactive isotope in a rock decays into a stable daughter isotope, used in absolute dating.