The landform that results when two normal faults cause valleys to drop down on either side of a block of rock is called a horst.

Here's a breakdown:

* Normal Faults: These are fractures in the Earth's crust where the hanging wall (the block above the fault) moves down relative to the footwall (the block below the fault).

* Horst: When two normal faults occur parallel to each other, they cause the block of rock between them to be uplifted, creating a raised block. The valleys on either side of this uplifted block are called graben.

So, the combination of a horst (uplifted block) and graben (down-dropped valleys) creates a distinctive landscape with alternating raised and lowered areas. This is a common feature in areas with extensive tectonic extension, like the Basin and Range Province in the western United States.