Stromatolites are large formations of rocks that have been formed by the growth of multiple layers of bacteria over a very long period of time. These usually take the shape of mounds, columns and sheets. Cyanobacteria, s... More »

The Virtual Fossil Museum states that Precambrian fossils mostly derive from organisms called stromatolites. Stromatolites are presumed to be among the world's oldest fossils. The existence of stromatolites is important,... More » History Prehistory

During the Precambrian Era, single-celled organisms, bacteria, microbes and some multi-cellular organisms existed. The Precambrian Era is split into the Hadean, Archaean and Proterozoic eons. More »

Sedimentary rocks are made of minerals and debris that have been weathered or eroded from rocks over long stretches of time. This sediment can be laid down by water, by the movement of earth or glaciers, by evaporation o... More » Science Earth Science Geology

The rock cycle explains the changes rocks undergo from the time they are expelled from the earth's mantle in the form of magma to the time that they return to the mantle and become magma once more. This process takes pla... More »

Geologists study the Earth and its physical formations and materials. This includes the layers of the earth, surface features like mountains and volcanoes and historical materials like rocks and fossils. More »

Citrine geodes are naturally occurring crystal formations that have a pronounced yellow or orange tint. The crystals inside the geode cavity are usually a form of amethyst that has been subjected to high temperatures by,... More » Science Earth Science Geology