Final answer:
We know about plate motion through seismic wave analysis, GPS data measuring Earth's crust, observing volcanic activity, and measuring Earth's magnetic field, each contributing valuable data to our understanding of plate tectonics.
Step-by-step explanation:
We learn about plate motion through several scientific methods. Seismic waves produced by earthquakes are crucial, as they provide information about the Earth's internal layers and their interactions. Changes in seismic wave velocities indicate the types and densities of materials they travel through, allowing us to understand plate boundaries and activity.
In addition, GPS data is used to measure the precise movements of the Earth's crust. By analyzing the data from global positioning satellites, geoscientists can calculate the rates and directions of plate tectonics. This real-time analysis is essential for understanding the dynamics of the Earth's surface.
The examination of volcanic activity is another way to learn about plate boundaries. Most volcanoes occur along plate boundaries, where plates either converge or diverge. Observing the patterns and locations of volcanic activity provides insights into the underlying tectonic motions. Lastly, the measurement of the Earth's magnetic field can reveal past plate motions, as new rocks formed at spreading centers record the Earth's magnetism at the time of their formation.