According to the Physics Department of the University of Tennessee Knoxville, evidence for plate tectonics has been found by studying continental shapes and comparing fossils. It notes that modern evidence for plate tectonics is much stronger than when it was first offered as a theory.
UTK notes that evidence of plate tectonics includes analyzing the continents as a whole picture. The continents resemble a jigsaw puzzle that has been separated, as can be seen by examining the coasts of North and South America and the west coasts of Africa and Europe. In addition, fossil evidence across multiple continents has indicated a species similarity that only makes sense if the different continents they were found on were once joined together. The University points out that along the original conjectured boundaries for tectonic plates, there is a large amount of geothermal, seismic and volcanic activity. This concentration of such activities serves as powerful evidence of both the existence and location of tectonic plates. Modern movement of the tectonic plates is seen in the still-growing Himalayas, where plates are pushing against one another. This is also seen in ridges such as the Mid-Atlantic Ridge where lava wells up between plates and separates them. The young age of the sea floor near these separated areas offers further proof of plate tectonics.