The Otira Gorge Viaduct in New Zealand, that carries a highway that crosses the Southern Alps, has its foundations in a deep layer of talus that has fallen off Hills Peak over centuries - that movement of rock being why they built the viaduct to replace the road - as the slope eroded the road had to be moved higher up the slope, adding more switchbacks to the infamous Zig Zag [0]. Plus the falling rock that made the road dangerous.
They were determined to hit bedrock, but yeah, was buried too deep. [1]
The fascinating thing about the Munich gravel plain is that it's really just a (very slightly inclined) plain - it's almost 100% flat, and the gravel is covered by a (relatively thin) layer of soil, so you could easily mistake it for the typical "lowlands" alluvial plain, and you'll probably be surprised to learn that it's at a height of ~400-700 m. So you don't really have to worry about the gravel moving - but it's still there...
However "alp" comes from Latin "Alpes", which is the mountain range in Western Europe we now call the Alps.
The word has become genericized to a degree. One the other hand Alps used to be one very specific mountain range, and alp a mountain in that mountain range, so surprise at some other place calling their mountain range Alps is understandable.
>surprise at some other place calling their mountain range Alps is understandable
yes, if you come from Wellington in Suffolk and you fly to Wellington in NZ, and then encounter that the nearby mountains are called Alps, you would be shocked, shocked
There is always bedrock, but in some places your pile would have to be really long to reach it:
> The gravel deposits of 100 m (330 ft) are the deepest in the south of Munich and decrease towards the north.
(from https://en.wikipedia.org/wiki/Munich_gravel_plain - not saying this is anything really extraordinary, but it's the area I'm most familiar with)