The large landmass that included all of Earth's present day continents
Alfred Wegener was a German meteorologist and geophysicist who noticed the similarity in the coastlines of eastern South America and western Africa and speculated that those lands had once been joined together
Continental drift
One of the earliest ways geologists thought continents moved over time, as hypothesized by Alfred Wegener
Wegener hypothesized that all of the modern-day continents had previously been clumped together in a supercontinent he called Pangaea
Wegener brought together several lines of evidence to support his theory of continental drift
Evidence of continental drift
Shape of the continents
Evidence from fossils
Evidence from landforms
Location of coal deposits
Evidence of climate
Wegener's theory of continental drift was rejected because his explanation was too weak and clashed with widely accepted ideas at the time
Alfred Wegener and his colleague Rasmus Villumsen died in a blizzard in Greenland in 1930
Almost 50 years later, HarryHess confirmed Wegener's ideas by using the evidence of seafloor spreading to explain what moved continents
Seafloor spreading
The continuous process of forming new igneous rock at midocean ridges by injection of magma that forms new seafloor
Sonar uses sound waves to detect underwater objects and determine underwater landforms and distances
Hess discovered the mid-Atlantic ridge and found the temperature near it was warmer, leading him to develop the theory of seafloor spreading
The ocean floor is difficult to explore due to the deep darkness, cold water, and high water pressure
The Earth does not get larger when new rock is added to the ocean floor at the mid-ocean ridge because the ocean floor is constantly being renewed
Continental crust is primarily composed of granite, a light-colored igneous rock rich in silica and aluminum.
Continental crust is thicker and less dense than oceanic crust, with an average thickness of about 35 km.