The characteristics that can be observed and measured in a sedimentary rock to deduce its depositional environment include its lithology (which is essentially its rock type), its sedimentary structures, and any fossils it may contain.

A fossil organism that is restricted to a particular rock, reflecting the original environment of deposition. From: facies fossil in A Dictionary of Ecology »

When the water level in the ocean basins is at a lower level than their capacity, the sea starts to expose the previously covered lands. The submerged seafloor is exposed as a result. This process is known as regression. All the changes we see are horizontal rather than vertical.

Types of depositional environments

• Alluvial – type of Fluvial deposite.
• Aeolian – Processes due to wind activity.
• Fluvial – processes due to moving water, mainly streams.
• Lacustrine – processes due to moving water, mainly lakes.

Few sedimentary rocks are found deep inside the Earth because sedimentary rocks form close to the surface of the Earth.

Examples include: breccia, conglomerate, sandstone, siltstone, and shale. Chemical sedimentary rocks form when dissolved materials preciptate from solution. Examples include: chert, some dolomites, flint, iron ore, limestones, and rock salt.

There are four types: lithogenous, hydrogenous, biogenous and cosmogenous. Lithogenous sediments come from land via rivers, ice, wind and other processes. Biogenous sediments come from organisms like plankton when their exoskeletons break down. Hydrogenous sediments come from chemical reactions in the water.

The main types of sedimentary rocks are clastic or chemical. Some sedimentary rocks are a third type, organic.

Oil, natural gas, coal, and uranium, our major energy resources, are formed in and come from sedimentary rocks. Sand and gravel for construction come from sediment. Sandstone and limestone are used for building stone. Rock gypsum is used to make plaster.

Chalk is a soft, white, porous, sedimentary carbonate rock, a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of sub-microscopic plankton which had fallen to the sea floor.

Thus, there are 4 major types of sedimentary rocks: Clastic Sedimentary Rocks, Chemical Sedimentary Rocks, Biochemical Sedimentary Rocks, and Organic Sedimentary Rocks.

Basalt is not a sedimentary rock. It is actually an igneous rock formed from cooled, melted rocks.

Rocks can explode in a campfire because of rapid expansion due to trapped water inside the rock, or through uneven heating. Although virtually all rocks have some amount of water inside them, porous and more permeable rocks have more water and are thus more dangerous inside a fire.

Basalt weathers faster than granite because it is not as hard and it’s easier for outside substances to impact and manipulate its structure.

Basalt is usually dark grey to black in colour, due to its high content of augite or other dark-coloured pyroxene minerals, but can exhibit a wide range of shading. Some basalts are quite light-coloured due to a high content of plagioclase, and these are sometimes described as leucobasalts.

On a chemical basis, basalts can be classified into three broad groups based on the degree of silica saturation. On this basis, most basalts consist predominantly of the normative minerals – Olivine, Clinopyroxene, Plagioclase, and Quartz or Nepheline.

‘A’a basalts have rough surfaces (that make barefoot people cry, “Ah! Ah!” as they walk across it). They form from fast flowing lava. Pahoehoe basalts have a smooth glassy surface that looks like many ropes.

: a dark gray to black dense to fine-grained igneous rock that consists of basic plagioclase, augite, and usually magnetite.

Fine-grained basic igneous rocks (basalts) The rocks of this group are predominantly found as extrusive lavas. Mineralogically they consist of plagioclase (An≫50) and pyroxene, with olivine also present in most.

Typical Imported Basalt In the way of explanation, apparent porosity could be described as the volume of pores which will readily absorb water under normal atmospheric conditions while total porosity is determined by ‘forcing’ water into the pores under a vacuum.