Continental Drift, Seafloor Spreading, and Plate Tectonics

Vocabulary practice cards focusing on key terms, figures, evidences, and plate boundary mechanisms from the Continental Drift, Seafloor Spreading, and Plate Tectonics lecture notes.

Alfred Wegener

German meteorologist and geophysicist who authored 'The Origin of Continents and Oceans' and proposed that all continents were once part of a supercontinent called Pangaea around $200\text{ MyA}$.

Pangaea

Meaning 'All Land', the supercontinent that existed approximately $200\text{ MyA}$ comprising all modern landmasses before they drifted apart.

Laurasia

The northern sub-landmass of Pangaea that included present-day North America, Europe, and Asia.

Gondwanaland

The southern sub-landmass of Pangaea that included modern-day South America, Africa, India, Australia, and Antarctica.

Panthalassa

Meaning 'All Sea', the single vast ocean that surrounded the supercontinent Pangaea.

Continental Shelf

Underwater land along continental margins used as a refined boundary to demonstrate jigsaw-like matching between continents, addressing critics' arguments about altered coastlines.

Mesosaurus, Glossopteris, and Lystrosaurus

Fossilized animals and plants found on now-separated continents, serving as evidence for Continental Drift because they could not have traversed wide oceans.

Appalachian-Caledonian Mountains

An example of matching rock types and geological mountain structures split across oceans, supporting the Continental Drift Hypothesis.

Paleoclimate Evidence (Continental Drift)

Geological evidence including coal seams from tropical trees located in cold Northern Hemisphere areas and glacial till/striations located near equatorial regions in Southern Africa, South America, Australia, and India.

Harry Hess

Geologist who introduced the Seafloor Spreading Theory in the early 1960s based on post-WWII ocean floor mapping.

Mid-Oceanic Ridges

The longest chains of underwater volcanoes, guyots, and seamounts where new oceanic crust is continuously formed and spread outward.

Apparent Polar Wandering

The observed shifting of magnetic poles recorded in rocks over time; distinct paths on different continents (such as Eurasia and North America) confirm that continents themselves drifted.

Normal Polarity vs. Reverse Polarity

Normal polarity occurs when Earth's magnetic north aligns with its geographic north; reverse polarity occurs when magnetic north aligns with geographic south, recorded as alternating magnetic stripes in oceanic crust.

Magnetic Reversals

Irregular flip-flops of Earth's magnetic poles over geological time, detected using a magnetometer as high-intensity (normal) and low-intensity (reverse) stripes, with the last reversal occurring $780,000\text{ years ago}$.

Hot Spot Volcanism

Localized, long-lasting hot regions below the lithosphere where a stationary mantle plume produces volcanic chains (e.g., Hawaiian chain and Emperor Seamount chain) as lithospheric plates move above it.

Hawaiian Chain Order

The sequence of volcanic islands formed over a hotspot ordered by age and motion: Kauai to Oahu to Molokai to Maui to Hawaii.

Wadati-Benioff Zone

A zone of seismic activity where hypocenter depth increases with distance from an oceanic trench, marking subducting slabs with deep earthquakes ($> 1590\,\text{km}$).

Plate Tectonics Theory

The unifying theory of geology finalized in 1967 stating that Earth's rigid lithosphere is divided into tectonic plates in continuous relative motion.

Divergent Boundaries

Constructive boundaries where plates pull apart, creating new oceanic crust at continental rifts and oceanic ridges.

Convergent Boundaries

Destructive boundaries where plates collide, causing subduction and remelting of oceanic lithosphere to form island arcs, volcanic arcs, or mountain systems (orogenic belts).

Transform Boundaries

Conservative boundaries where two plates slide horizontally past each other, connecting ocean ridge systems without creating or destroying crust.

Island Arc vs. Volcanic Arc

An Island Arc forms from oceanic vs. oceanic lithosphere subduction, whereas a Volcanic Arc forms from oceanic vs. continental lithosphere subduction.

Mantle Convection

A major driving force for plate movement where density and temperature differences cause hotter, less dense mantle material to rise while cooler, denser material sinks.

Philippine Mobile Belt and Philippine Fault Zone

Geologic structures formed by oceanic vs. oceanic convergent plate boundary activity within the Philippine tectonic setting.

Palawan Microcontinental Block

A continental block involved in continental vs. oceanic convergence in the Philippines, notable for being free of earthquakes compared to the rest of the region.