Sedimentary rocks

Notice in the figure below that the rock is formed by layers (or strata).

This type of rock is called sedimentary rock and forms from changes in other rocks.

Wind rain, river water, sea waves: all of these gradually break the rocks into mineral grains. Little by little, over thousands of years, even the most solid granite turns into small fragments. This process is called weathering.

Rock fragments are carried by winds or rainwater to rivers, which in turn carry them to the bottom of lakes and oceans. There the fragments are deposited in layers. This is how, for example, sand-covered terrain is formed, such as beaches.

These fragments or sediments accumulate over time. The top layers exert pressure on the bottom layers, compressing them. This pressure ends up grouping and cementing the fragments and hardens the mass formed. this is how sedimentary rocks arise. All this, don't forget, takes thousands of years.

In this way, the sand of the beach slowly turns into a sedimentary rock called sandstone. Clay sediment turns into clayite.

The layers also cover the remains of plants and animals.

So it is very common to find animal or plant remains or marks on sedimentary rocks: the animal or plant dies and is covered by thousands of mineral grains.

The remains or marks of ancient organisms are called fossils. By analyzing the fossils, scientists can study what life was like in the past on our planet.

Sedimentary Rock Formation

The origin of sandstone

Sandstone forms when rocks such as granite gradually disintegrate due to wind and rain. The quartz grains of these rocks form the sand. Sands and sand dunes, but they are not rocks: they are fragments of rocks. The sand may settle on the sea floor or in depressions and be subjected to increased pressure or temperature. Thus cemented and hardened, it forms the sandstone - a type of sedimentary rock. Sandstone is used in floors.

Sandstone Rock

Sand Dunes in Death Valley, California


The accumulation of skeletons, shells and carapaces of salt-rich calcium carbonate aquatic animals can form another variety of sedimentary rock, limestone.

Limestone also forms from deposits of calcium salts in water. Limestone is used in the manufacture of cement and lime. Lime is used for wall painting or paint manufacturing. Lime or limestone itself can be used to counteract the acidity of soils.

Limestone waterfalls in Turkey, Aegean.