Why are historical sites and artifacts always found buried?

Question

Ancient cities always seem buried under may feet of earth. How does this occur?

Answer 1

It is evidence for erotion and deposition. Depending on local conditions, areas erode away or get covered by sediments. If a ruin is in a area that is getting deposition, then it can get covered and we can dig it up later. If a ruin is in an area that is being eroded, it is destroyed and dispersed.

Answer 2

there is evidence that energy from the Earth's accumulation caused the surface to be molten. Further, the processes of erosion and crustal recycling have apparently destroyed all of the earliest surface (from http://www.talkorigins.org)

It is also because the walls of the structures collapse by time and the winds and storms along with rain and floods drag all the sands over the remnants. Besides hard materials such as stone, marble etc used in the construction of the structure get corroded by the time.
Some cities like pompei got lost under the lava errupted from a volcano.
However not all the cities or structures are buried under the earth such as pyramids.

Answer 3

Not all historical sites had been buried, many examples in historical cities(Rome, Athen's acropolis) but usually is so because detrites accumulate and the ground level grows. And because buried artifacts are protected while artifacts that stay outside are easily destroyed (especially if built in fragile materials like wood).

Answer 4

Junk and dirt tends to collect and cover things up. Also depending on the soil composition, ruins can sink.

Answer 5

Sedimentation.

Answer 6

The wind blew dirt over them after they were abandoned.