Short Answer 
The calculation of tectonic plate motion involves three steps: first, determine the total distance moved in millimeters, then calculate the rate of motion by dividing the distance by the number of years, and finally, predict future movements based on the annual rate. For instance, if a plate moves 125,000 meters over 25 million years, it translates to a rate of 5 mm/year, suggesting it could move 5,000 meters in the next million years.
Step 1: Determine the Distance Moved
First, calculate the total distance that the tectonic plate has moved over a given period of time. Since the motion is measured in millimeters per year, you’ll want to convert any distances you have into the same unit. Use the conversion factor of 1 meter = 1,000 millimeters to achieve this. For instance, if the plate is said to have moved 125,000 meters, you will convert it to millimeters:
- 125,000 meters * 1,000 = 125,000,000 millimeters
Step 2: Calculate the Rate of Motion
Now that you have the total distance in millimeters, you can find the rate of motion. To do this, divide the distance moved by the number of years over which the movement has occurred. For example, if the plate has moved 125,000,000 millimeters over 25,000,000 years, the formula would be:
- Rate of motion = 125,000,000 mm / 25,000,000 years = 5 mm/year
Step 3: Predict Future Movements and Geology Changes
Finally, you can use the rate of motion to predict how far the plate will move in the future. To forecast movement over, say, 1 million years, multiply the annual rate by the number of years:
- 1,000,000 years * 5 mm/year = 5,000,000 mm
- 5,000,000 mm / 1,000 = 5,000 meters