Flood basalt

Trapp ( stairs) is the old, dating from the Scandinavian term for step-like formations from flood basalt (or other igneous rocks, such as diabase or melaphyre ), extending over part of huge areas. Actually, there are numerous superimposed blanket-like formations, in each of which an upper over the lower back occurs with a vertical drop.

Well-known examples are the Deccan Traps in India and the Siberian Trapp in Russia.

The term is now no longer used as a geological term, but only as historically evolved Name geographical occurrence.