Humans have pondered the mysteries of Earth’s ground movements since the dawn of recorded history After all earthquakes have been rumbling and volcanoes have been erupting for longer than humans have been around to witness them So what makes the ground move or shake What makes a mountain explode with fiery fury Scientific understanding and theories concerning the forces that cause volcanic eruptions and earthquakes have grown immensely in the past 100 years 6
As a scientific theory plate tectonics is built upon previous theories proven to be scientific facts Scientists then test new theories in an ongoing effort to advance collective scientific knowledge Until early in the 20th century much of the study of Earth’s physical surface assumed the planet’s continents were stationary But one feature of Earth’s modern continental map made some scientists revisit this theory Africa South America The opposite coasts of Africa and South America almost look like puzzle pieces that fit together This led some scientists to wonder as early as the late 1500’s if the two could have broken apart from one another by a series of disastrous floods or earthquakes 8 8
PLATE TECTONIC PIONEER In 1912 German scientist Alfred Wegener put forth the theory of continental drift His theory was based on fossil evidence that showed the existence of the same plants and animals on separate continents in differing climates Since they could not have crossed the ocean as living organisms Wegener reasoned the continents had once been joined He theorized that over millions of years the continents had drifted to their current locations Wegener could not identify the forces causing the movement and his theory was largely ignored during his lifetime After his death the theory of continental drift would spark the scientific discoveries leading to the current understanding of plate tectonics Eurasia Africa India North America South America Antarctica Australia Wegener’s continental drift theory included his assertion that all present-day continents were once a single land mass he called Pangea meaning all Earth 9 9
