Final answer:
The Himalayan mountains are expected to increase in height due to the continued collision of the Indian and Eurasian tectonic plates, despite erosion processes.
Correct option is c. Increase due to continued collision
Step-by-step explanation:
If the plate motion remains the same, the height of the Himalayan mountains over the next 1 million years will likely increase due to continued collision. This is because the Indian tectonic plate is constantly pushing northward into the Eurasian plate, which forces the Himalayan ranges upward. Despite the fact that erosion occurs, this geological process cannot counterbalance the significant uplifting effect caused by plate tectonics.
Additionally, the process of mountain building, also known as orogeny, is ongoing in the region. This, coupled with the fact that plates can move up to an inch a year in active regions like the Himalayas, suggests that the collision between the tectonic plates will continue to push the mountains higher as long as the current rate of movement is maintained.