The sedimentary rocks that form when broken down by weathering and erosion and then compacted together under pressure are called clastic sedimentary rocks.

Here's a breakdown of the process:

1. Weathering and Erosion: Rocks are broken down into smaller pieces (clasts) by weathering (physical and chemical processes) and erosion (transportation of those pieces).

2. Transportation and Deposition: The weathered and eroded fragments are transported by wind, water, or ice, and eventually deposited in a new location, often in layers.

3. Compaction and Cementation: Over time, the weight of overlying sediment compacts the layers, squeezing out water and air. Dissolved minerals in the water precipitate and crystallize between the clasts, cementing them together.

Examples of clastic sedimentary rocks include:

* Conglomerate: Composed of large, rounded clasts (gravel-sized).

* Breccia: Similar to conglomerate but with angular clasts.

* Sandstone: Made of sand-sized grains.

* Siltstone: Composed of silt-sized particles.

* Shale: Made of very fine clay-sized particles.

Let me know if you have any other questions about sedimentary rocks!