What was unknown to scientists during Wegener's time?
A - Earth's crust is made of plates that move
B - The coasts of some continents fit together
C - Fossils were found in many places
D - Mountain ranges of some continents lined up
A - Earth's crust is made of plates that move
The correct answer is A - Earth's crust is made of plates that move. During Wegener's time, scientists were not aware that Earth's crust is made of plates that move. This concept, known as plate tectonics, suggests that the Earth's surface is divided into several large plates that are in constant motion, leading to various geological phenomena such as earthquakes, volcanic activity, and the shifting of continents. Wegener's theory of continental drift, which proposed that continents had drifted apart over time, was initially met with skepticism because the mechanism of plate tectonics had not yet been discovered. It was not until the mid-20th century that the theory of plate tectonics gained widespread acceptance and provided a comprehensive explanation for many geological processes.
During Wegener's time, the concept of Earth's crust being made of plates that move, known as plate tectonics, was unknown to scientists. Therefore, the correct answer is A - Earth's crust is made of plates that move.
To understand how scientists came to discover plate tectonics, it is important to know about Alfred Wegener's theory of continental drift, which was proposed in the early 20th century. Wegener noticed that the continents appeared to fit together like puzzle pieces, particularly along the eastern coastlines of South America and Africa. He also observed similarities in rock formations, mountain ranges, and fossils on both continents.
While Wegener's observations were significant, he did not have a comprehensive explanation for these phenomena. His theory faced criticism and skepticism from the scientific community at that time, largely due to the lack of a plausible mechanism to explain how continents could move across the Earth's surface.
It was not until the mid-20th century that advancements in technology, such as advances in seismology and the mapping of the ocean floor, provided substantial evidence for the theory of plate tectonics. Scientists discovered that the Earth's crust is composed of several rigid plates that float on the semi-fluid layer below called the asthenosphere. These plates slowly move and interact with each other, causing geological phenomena like earthquakes, volcanic activity, and the formation of mountain ranges.
In conclusion, during Wegener's time, scientists were unaware of plate tectonics and the idea that Earth's crust is made of plates that move. It was only later with advancements in technology and scientific understanding that plate tectonics became a widely accepted theory.