Sediments may be compressed and heated to form sedimentary rocks, while sedimentary rocks are eroded in turn and weathered to form yet more sediments.
When you look at sedimentary rocks, the ones on the bottom are the oldest, because the rocks are laid down in order as sediments that later harden into rock.
Sedimentary rocks are formed when sediments are covered, compressed and heated to some extent, so the grains of sediment become cemented together.
The oldest sediments contain the oldest fossils, so lower sedimentary rocks contain older fossils. This provides some of the evidence for evolution.
In 1669 Steno, in his 'Prodromus', suggested that tilted strata of geology were originally laid down horizontally, and were later lifted up by some force.
When sediment is carried to the front of an advancing bank of sediment and pushed over the edge, it forms a characteristic slope at the angle of repose or rest.
Sediments are laid down in strata, comparatively horizontal layers, except in cross-bedding or current bedding, when they are laid at the angle of rest.
When sediment forms a slope at the angle of repose, this angle is determined mainly by the shapes of the particles and the medium (air or water) of deposition.
When sediment is pushed down a slope at the angle of repose, it forms a bed laid down at that angle, rather than horizontal. This is current bedding.
Wind transports sediment, but generally over short distances only, unless the particles are fine. Dust particles may be carried from one continent to another.
Fine sediments can be carried long distances by wind: from Australia across to New Zealand, from China to the US or from the Sahara to the US in proven cases.
The sediment particle size depends on the speed of the wind or water flow, and coarser sediment settles as the speed drops away, producing graded deposits.
Glaciers transport sediment, picking up rocks and grinding them across the countryside, producing 'rock flour' along the way, and washing it out in meltwater.
Glaciers may move and create sediment throughout the year, but more sediment is released in summer when the ice melts more and the meltwater flows increase.
The seasonal variation each year in the flow of meltwater from the head of a glacier produces varved deposits, which later may be compressed to varved shales.