How do sedimentary rock layers form?

Answer 1

Sedimentary rocks are formed because of the overburden pressure as particles of sediment are deposited out of air, ice, wind, or water flows carrying the particles in suspension. As sediment deposition builds up, the overburden (or 'lithostatic') pressure squeezes the sediment into layered solids in a process known as lithification ('rock formation') and the original connate fluids are expelled. The term diagenesis is used to describe all the chemical, physical, and biological changes, including cementation, undergone by a sediment after its initial deposition and during and after its lithification, exclusive of surface weathering.

Sedimentary rocks are laid down in layers called beds or strata. Each new layer is laid down horizontally over older ones in a process called superposition. There are usually some gaps in the sequence called unconformities. These represent periods in which no new sediments were being laid down, or when earlier sedimentary layers were raised above sea level and eroded away.

Sedimentary rocks contain important information about the history of the Earth. They contain fossils, the preserved remains of ancient plants and animals. The composition of sediments provides us with clues as to the original rock. Differences between successive layers indicate changes to the environment which have occurred over time. Sedimentary rocks can contain fossils because, unlike most igneous and metamorphic rocks, they form at temperatures and pressures that do not destroy fossil remnants.

The sedimentary rock cover of the continents of the Earth's crust is extensive, but the total contribution of sedimentary rocks is estimated to be only five percent of the total. As such, the sedimentary sequences we see represent only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks.

Answer 2

Sediments like mud or sand are deposited in layers, one on top of the other, by wind or water (and sometimes by landslides). Over time, they get lithified (turned into rock) by getting the grains compressed together by the weight of the layers over top of them, and/or "glued" together with minerals (such as calcium) in groundwater or other sources.

Answer 3

Sediments = minerals that settled.

Answer 4

they are formed from mineral settings