Natural Hazards, Continental Drift, and Plate Tectonics

Vocabulary flashcards covering the distinction between natural hazards and disasters, human vulnerability factors, Alfred Wegener's Continental Drift Theory and its evidence, and the mechanics and boundary types of Plate Tectonics.

Natural Hazard

A naturally occurring physical event (such as an earthquake, volcanic eruption, or tsunami) that has the potential to cause harm to people or property.

Natural Disaster

The realization of a hazard that causes major disruption to a community, resulting in widespread human, material, economic, or environmental losses that exceed the community's ability to cope using its own resources.

Vulnerability

The conditions determined by physical, social, economic, and environmental factors that increase the susceptibility of a community to the impact of hazards.

Continental Drift Theory

The concept developed and explained by Alfred Wegener in the early 20th century proposing that the continents are not fixed in one place, but have slowly moved over millions of years.

Pangaea

The single supercontinent that once joined all continents together before it began breaking apart about 250 million years ago.

Panthalassa

The vast single ocean that completely surrounded the supercontinent Pangaea.

Laurasia

The northern supercontinent formed after Pangaea split, comprising mainly North America, Greenland, and Eurasia.

Gondwanaland

The southern supercontinent formed after Pangaea split, comprising South America, Africa, Antarctica, India, and Australia.

Jigsaw Fit (Juxtaposition)

A piece of geological evidence for continental drift showing that the shapes of separated continents, such as South America and Africa, fit together like pieces of a puzzle.

Mesosaurus

A prehistoric reptile whose identical fossils were discovered in both Brazil and South Africa, providing evidence that these distant landmasses were once connected.

Glossopteris

An ancient plant whose fossils have been identified across India, Australia, South Africa, Antarctica, and the Falkland Islands, supporting continental connection.

Lithosphere

The Earth's rigid outer shell that is broken into large pieces known as tectonic plates.

Asthenosphere

The semi-fluid layer beneath the lithosphere across which tectonic plates travel due to convection currents in the mantle.

Divergent Boundaries (Constructive)

Plate boundaries where tectonic plates pull apart, creating new crust and resulting in geological features like mid-ocean ridges, rift valleys, gentle effusive basaltic eruptions, and shallow mild earthquakes.

Subduction (Convergent Boundary)

The process at oceanic-continental or oceanic-oceanic convergent boundaries where the denser oceanic plate plunges beneath the lighter plate into the mantle, destroying crust and leading to explosive volcanoes, deep/shallow earthquakes, and tsunamis.

Continental-Continental Collision

A convergent boundary interaction where two continental landmasses collide and buckle upward into fold mountains (such as the Himalayas), causing shallow-to-moderate severe earthquakes without volcanic activity.

Transform Boundaries (Conservative)

Plate boundaries where plates slide horizontally past one another, leaving crust neither created nor destroyed and producing frequent, high-magnitude shallow earthquakes with no volcanic activity.