What type of rock is formed by the accumulation of organic material and sediment?

The formation of sedimentary rock is primarily a result of the accumulation of organic materials, such as plant and animal remains, along with various sediments over time. These materials settle in layers, commonly in environments like riverbeds, lakes, and ocean floors. Over long periods, the weight of additional sediments compacts the accumulated layers, and minerals precipitate from water, cementing the particles together.

Sedimentary rocks often exhibit features that reflect their origins, such as fossils or distinct layering, which provide valuable information about the Earth's history and past environments. This type of rock can also form through chemical processes and the precipitation of minerals from water, but the common link remains the accumulation of materials that include both organic and inorganic components.

In contrast, igneous rocks result from the cooling and solidification of molten rock (magma or lava), metamorphic rocks form from the alteration of existing rocks through heat and pressure, and volcanic rocks are a subset of igneous rocks that specifically form from volcanic activity. None of these rock types involve the direct accumulation of organic material and sediment like sedimentary rocks do.