Done tons of research but can't square some conflicting evidence on the past (480 bc) vs current area of Thermopylae. I believe it's common knowledge that alluvial fans/deposition has resulted approximately 20 meters of sediment deposited over the battlefield (specific to 480 bc). I also believe it's commonly accepted that the pass was roughly 15-30 meters wide with shear cliffs on the southern side and a drop (height unknown, but not substantial) to the sea below on the north side. Additionally, the Phocian Wall, of which the remains are still visible, was thought to be approximately 3-4 meters tall.

My questions are:

1. If there is anywhere near 20 meters (~66 feet) of deposition covering the battlefield, how can a 4 meter (12 foot) wall still be visible? Even with a margin of error on both sides, these two statements can't both be true at the same location. Additionally, archeologist state only the base of the Phocian wall remains, which means it certainly can't be buried under 60 feet of sediment and at the same level it was when built pre-480 bc.
2. Along these same lines, the wall is roughly 150 meters (500 feet) long. According to most geologist (plenty of solid university data on the web), although the sediment deposited has resulted in a large plain now, 2,500 years ago the pass was likely no more than 100 feet wide (that's the upper limit) - most think less than 40 feet). If what is believed to be the Phocian wall is in fact that wall, it wouldn't extend roughly 500 feet (even diagonally) at the same elevation, which it does. Again, even with some significant margins on both sides here, there isn't room for a 500 foot wall on a 50+ foot width.

Between the length of the accepted wall vs the width of the pass at the time, and the known deposition of 60+ feet of sediment vs a visible wall at the surface, I don't see how this can be the actual wall spoken of during the battle. Can't seem to find anyone else asking these questions, so posting here. Thanks all.