Geology Times (Part 2) - 1403

## دوران های زمین شناسی ### A. Precambrian or Cryptozoic 1. **Hadeon** - The **Hadeon** era spans from the formation of the solar system to the oldest known rocks on Earth's surface. - The Earth and other planets in the solar system likely formed within the first 100 million years of this...

## دوران های زمین شناسی ### A. Precambrian or Cryptozoic 1. **Hadeon** - The **Hadeon** era spans from the formation of the solar system to the oldest known rocks on Earth's surface. - The Earth and other planets in the solar system likely formed within the first 100 million years of this era. - The Earth's crust started to form, and its thickness increased during this time. - The Hadeon era saw the formation of large oceans, dry plains, mountain ranges, valleys, rivers, volcanoes, thick clouds and strong winds. 2. **Archean** - The oldest rocks on Earth mark the beginning of the **Archean** era, which lasted from 4000 to 2500 million years ago. - The most notable events of this era are biological changes. - Perhaps the most significant biological molecule developed during this time was chlorophyll, which allowed early life forms to produce their own food. - The first photosynthetic organisms, cyanobacteria, appeared. 3. **Proterozoic** - The **Proterozoic** era lasted from 2500 million years ago to about 542 million years ago, marking a period when life significantly expanded on Earth. - The **Proterozoic** era is divided into three sub-eras: Paleoproterozoic, Mesoproterozoic, and Neoproterozoic. - Notable events of this era include the formation of an oxygen-rich atmosphere on Earth during the Mesoproterozoic and the occurrence of numerous ice ages. ### B. Paleozoic 1. **Cambrian** - The **Cambrian** period is divided into three sub-periods: lower, middle, and upper. - The **Cambrian** period lasted from 570 to 510 million years ago. - Glacial deposits in **Cambrian** sedimentary rocks in China and other locations indicate a cold climate during this time. 2. **Ordovician** - The **Ordovician** period derives its name from the Ordovician tribe that lived in Gaul. - This period lasted from 515 to 438 million years ago. - Several organisms became extinct at the end of the **Cambrian**, including trilobites. - Graptolites (transitional creatures between vertebrates and invertebrates) with spine-like structures are prominent in this period. - The climate during the **Ordovician** period was warmer than the **Cambrian**, with more limestone and dolomite deposits. - Petroleum deposits from the **Ordovician** period suggest the abundance and development of microscopic organisms in the oceans of that time. - Significant evidence exists of mass extinctions at the end of this period. 3. **Silurian** - The **Silurian** period is named after the Silures tribe, who inhabited southwestern England. - It is the shortest **Paleozoic** period, with its duration estimated to be between 28 and 34 million years (from 438 to 410 million years ago). - The lower boundary of this period is identified by a specific type of graptolite fossil. - Similarly, the upper boundary of the **Silurian** is marked by a graptolite zone. - The **Caledonian Orogeny** occurred at the end of the **Silurian** period, affecting a large area of northern Europe, leading to a decrease in ocean size and an increase in landmass. 4. **Devonian** - The **Devonian** period lasted from 408 to 360 million years ago. - It lies between the **Caledonian** and **Hercynian** orogenic periods. - The lower part of the **Devonian** includes **Old Red Sandstone**. - Marine transgression during this period led to an increase in coral reefs. - These coral reefs formed in relatively calm environments, away from swampy areas. - The **Devonian** period is known as the Age of Fishes. - The first insects appeared during this period. - Terrestrial plants, including vascular cryptogams, flourished during this period. - The widespread presence of limestone and evaporite deposits indicates a warm climate during this period. 5. **Carboniferous** - Carboniferous layers in England were named **Carboniferous** in 1882. - This period lasted from 360 to 299 million years ago. - In America, the deposits corresponding to this period are known as the Mississippian and Pennsylvanian periods. - The presence of coal layers indicates a warm and humid climate during this period. - Significant orogenic movements took place during this period, leading to the formation of the **Hercynian** mountain range. - The growth and development of plants reached their peak during the **Carboniferous** period. - Fossils of gymnosperms and vascular cryptogams are found in **Carboniferous** coal-bearing deposits. 6. **Permian** - The **Permian** period was first applied to marine deposits from the late **Paleozoic** period found in the Perm region of eastern Russia. - This period lasted from 299 to 252 million years ago. - In some locations (e.g., Jalfa and Araz on the border of Iran and Russia), the transition between the **Permian** and the **Triassic** periods is not clear, and the combination of these deposits is known as **Permotriassic**. - Two main types of deposits characterize the **Permian:** marine and continental. - One of the notable characteristics of the **Permian** period is the presence of widespread glacial developments in various regions around the world. - There is evidence of reptiles from the **Permian** period. - During the **Permian** period, the major landmasses of Earth merged to form the supercontinent, **Pangea**. - By the end of the **Permian** period, 75% of amphibian families and many plant types became extinct. ### C. Mesozoic 1. **Triassic** - The **Mesozoic** era (meaning "middle life") is subdivided into three periods and lasted for 186 million years. - The evolution of giant reptiles, (dinosaurs), and ammonites (cephalopods) marks this period. - The climate of the **Mesozoic** era was generally warm and tropical, more uniform than the climate we see today. 2. **Jurassic** - The **Triassic** period, named after the Alps by Albertini in 1834, marks the transition to the **Jurassic**, - It is considered the "golden age of dinosaurs." - The most notable development in the **Jurassic** was the appearance of birds. - There was a significant increase in the number of reptiles, particularly dinosaurs. - The **Jurassic** is known for its vast deposits of coal and oil, indicating widespread swampy conditions. - Notable events of this period are the breaking up of the supercontinent, **Pangea**, into several smaller continents and the appearance of the Pacific Ocean. - The **Jurassic** period also witnessed the development of flowering plants, coniferous trees, and gymnosperms. 3. **Cretaceous** - The **Cretaceous** period, named after creta, the Latin word for chalk, is the longest and the final period of the **Mesozoic** era, lasting from 145 to 66 million years ago. - The end of the **Cretaceous** period marks the end of the dinosaurs. - Chalk deposits are common in the **Cretaceous** period and represent the remains of microscopic algae (coccolithophores). - The end of the **Cretaceous** period is characterized by mass extinctions and a major geological event, the **Albian-Cenomanian Oceanic Anoxic Event**, which resulted in widespread oceanic anoxia - It is characterized by the dominance of *ammonites* and *belemnites*. ### D. Cenozoic 1. **Paleogene** - The **Paleogene** (formerly called Tertiary) period lasted from 66 million years ago to 23 million years ago, marking the beginning of the Cenozoic Era. - During this period, mammals evolved from simple, smaller forms into diverse and larger groups. - Birds also significantly evolved during this period, approaching their modern forms. 2. **Neogene** - This period lasted from 23 million to 2.6 million years ago. - The **Neogene** is characterized by the continued evolution of mammals and birds. - The ancestors of modern humans emerged in Africa during this period. - Several continental shifts occurred during this time, including the joining of North and South America through the Panama Isthmus in the late Pliocene, which had a major impact on global ocean currents, leading to the development of the Gulf Stream. - Global temperature during this period decreased, leading to several continental glaciations in the Quaternary period. 3. **Quaternary** - The **Quaternary** period, the youngest period in geological history, spans from 2.6 million years to the present. - Some geologists refer to it as the **Plio-Quaternary**. - The **Quaternary** is marked by the continuation of the Alpine orogeny that started during the Pliocene. - Glaciers were widespread during this period, known as the "Ice Age," covering much of northern Europe, Canada, and a significant portion of North America. - Humans emerged during the **Quaternary** period. Some geologists and paleontologists refer to it as the "Age of Man" or **Anthropozoic**. The **Quaternary** period is characterized based on fossils of early humans. ### Reasons for Dinosaur Extinction Scientists have proposed several explanations for the extinction of dinosaurs. One prominent theory posits that an asteroid impact about 65 million years ago triggered a mass extinction event. The asteroid, estimated to be five miles in diameter, struck Earth at a speed of 150,000 miles per hour, with an explosive force equivalent to 100 million megatons of TNT. This collision created a massive dust cloud composed of debris from the asteroid and pulverized Earth materials, obscuring sunlight and leading to a global cooling over several years. This event, combined with the prolonged darkness, catastrophic changes in the climate, and the massive release of toxic gases and materials, led to the demise of various plant and animal life, including the dinosaurs.