This process called continental drift , actually shapes the Earth's surface, continents, mountain ranges, etc. Notice that the plates do not match the continents. Some plates are drifting apart. In those cases, fresh material from the mantle upwells to fill in the space. This happens for example in the middle of the Atlantic ocean.
Some plates collide head on.
The forces driving the plates continuous and so strong that the collision doesn't stop the plates. Instead, the plates keep pushing against each other crushing themselves. This happens for example at the Himalayas, and at the Andes, creating two of the largest and highest mountain ranges on Earth. Some plates that collide head on don't crush each other with equal force. Instead, one plate ends up sliding under the other plate.