Mesoproterozoic

The Mesoproterozoic Era is a major period in Earth's geologic history. It is the first era where a fairly definitive geological record survives. Before this era, during the Paleoproterozoic, continents already existed. However, scientists know very little about those earlier land masses. The continents of the Mesoproterozoic were mostly the same as today's continents. Their arrangement on the Earth's surface was simply different. This era provides a vital window into how our planet's crust behaves.

Plate tectonics drove many massive changes during this time. Plate tectonics is the movement of large pieces of Earth's crust. One major event was the breakup of the Columbia supercontinent. This massive land mass split apart between 1500 and 1350 million years ago. Later, the resulting fragments reassembled into a new supercontinent called Rodinia. This formation of Rodinia happened between 1100 and 900 million years ago. This occurred near the boundary of the next era, the Neoproterozoic.

These shifting plates also caused many orogenies. An orogeny is an episode of mountain building. Many different orogenies occurred across the globe during this era. In Africa, the Kibaran orogeny took place. The Late Ruker orogeny occurred in Antarctica. Europe experienced the Gothian and Sveconorwegian orogenies. North America saw the Picuris and Grenville orogenies. These events show how much the Earth's surface changed.

Life also underwent significant transformations during the Mesoproterozoic. The era saw the evolution of sexual reproduction. This biological process helped increase the complexity of future life. It also marked the start of true multicellular organisms. While scientists once thought life was only microbial, recent finds prove otherwise. Multicellular life did exist during this era. Additionally, stromatolites reached a high point during this period. These structures declined later in the Neoproterozoic.

Scientists divide the Mesoproterozoic into three specific subdivisions. These divisions are based on time rather than rock layers. They are not considered geostratigraphic or biostratigraphic units. The Calymmian period lasted from 1600 to 1400 million years ago. The Ectasian period lasted from 1400 to 1200 million years ago. The Stenian period lasted from 1200 to 1000 million years ago. These time scales help researchers organize the era's history.

Each subdivision has its own unique geological characteristics. The Calymmian and Ectasian periods were defined by certain stability. They featured the stabilization and expansion of cratonic covers. A craton is a stable part of a continental plate. In contrast, the Stenian period was different. It was characterized by the formation of orogenic belts. These belts are long chains of mountains. This shows how the Earth's crust changed over millions of years.

Researchers use radiometric dating to define these Precambrian subdivisions. This method uses the decay of atoms to find ages. It is used because the fossil record is often sparse. Some scientists use an unofficial period called the Rodinian. This period spans from 1780 to 850 million years ago. It is based on stratigraphy rather than chronometry. However, the International Union of Geological Sciences has not officially adopted it. Future revisions may create more natural boundaries based on geologic events.