Earth’s Geological History

Origin of Earth 4.6 billion years ago The sun and the planets coalesced out of a vast cloud of gas and dust The Earth was a hot glowing ball of white hot gases. Particles of gases were compressed together, giving off heat. Gases cooled down so the Earth contracted and gases turned to liquids. Heavy materials went to the center of the Earth and a liquid material went to the center.

The Moon 4.527 billion years ago A large impact on Earth heated up and was flung into space into the orbit of the Earth. The moon’s gravitational pull might have made Earth a livable planet by making the Earth’s axial tilt constant, which made the Earth keep a stable climate.

Moon’s Formation According to the "giant impact" theory, the young Earth had no moon. At some point in Earth's early history, a rogue planet, larger than Mars, struck the Earth in a great, glancing blow. Instantly, most of the rogue body and a sizable chunk of Earth were vaporized. The cloud rose to above 13,700 miles (22,000 kilometers) altitude, where it condensed into innumerable solid particles that orbited the Earth as they aggregated into ever larger moonlets, which eventually combined to form the moon.

The Creation of the Moon A plant like object crashed into the earth and part of it shifted away About 4.527 billion years ago

History of the Earth The Earth's crust, its outermost layer, formed about 4.44 billion years ago, roughly 100 million years after the formation of the Earth itself. Prior to 4.44 billion years ago, the Earth's crust was entirely molten, due to residual heat from the planet's initial collapse. Evidence that the Earth's crust cooled within 100 million years comes from measurements of hafnium levels in the Jack hills in Western Australia, one of the oldest areas of exposed crust today. During the initial formation of the Earth's crust, an event known as the Iron Catastrophe occurred, where the denser elements of the Earth's composition, such as iron and nickel, sank to its core, while the lighter elements, like silicon, formed a crust at the top. The crust began to cool when the Earth was at least 40% of its current size, possessing enough gravity to hold down an atmosphere containing water vapor. Much of this early water vapor would have come from comets.

Ancient landscape Massive volcanoes and lava fields dominated the landscape

Water Was Formed On Earth About 3.8 billion years ago The crust formed over the liquid material. The crust cracked, revealing water underneath and water vapor was formed. Water vapor formed clouds and water was pulled towards Earth’s surface in rainfall making lakes and oceans.

Life on Earth 3.5 billion years ago Scientists think that the first single cell organisms lived near hydrothermal vents in the oceans because of the chemicals by the vents. 3 500 million years ago Prokaryotes were started. 1 800 million years ago Complex single-celled life appears. 1 500 million years ago Eukaryotic cells appear. 1 000 million years ago Multicellular organisms appear.

Photosynthesis 3.4 billion years ago First photosynthetic bacteria appeared. They absorbed near-infared instead of visible light and produced sulfur or sulfate compounds instead of oxygen. 2.7 billion years ago Cyanobacteria was the first of the oxygen producers. They used light to produce oxygen.

Stable Continents Appear About 2500 million years ago The surface of the Earth was cooled, re-melted, and solidified again. The landmasses would come together and then drift apart again. Plates broke apart and drifted away, forming today’s continents.

Ozone Layer About 1600 million years ago The formation of ozone layer starts blocking ultraviolet radiation from the sun. This allowed life to start to appear on the land. The ozone is a form of oxygen.

Snowball Earth About 700 million years ago Earth was a planet covered by glacial ice from pole to pole. The temperature would be about -74 degrees. Solar radiation would be reflected back to space by the icy surface. In time, glacial ice would thicken and flow in the opposite direction which would leave sediments behind.

Snowball Earth The coldest global climate imaginable - a planet covered by glacial ice from pole to pole. The global mean temperature would be about -50°C (-74°F) because most of the Sun's (Solar) radiation would be reflected back to space by the icy surface. Despite the cold and dry climate, the atmosphere would still transport some water vapor from areas of sublimation (direct change from solid to vapor) to areas of condensation. Given sufficient time, glacial ice would thicken and flow in the opposite direction. Glacial flowage resulted in sedimentary deposits

Mass Extinction About 650 million years ago There was a mass extinction of 70% of dominant sea plants. The extinction was caused by global glaciation.

First Soft-Bodied Organisms 580 million years ago Soft body organisms started developing These organisms were the jelly fish, tribrachidium, etc.

Geological Timeline

Precambrian 4,500-550 mya The Precambrian is an informal name for the supereon comprising the eons of the geologic timescale that came before the current Phanerozoic eon. Stromatolites First single-celled organisms, simple plants, and invertebrate animals: algae, bacteria, jellyfish, flagellates, amoebas, worms, sponges 4,500-550 mya (millions of years ago)

Cambrian Period 550-505 mya Stromatolites First trilobites, forams, brachiopods, nautiloids, clams, snails, crustaceans, crinoids, gastropods, corals, protozoans The Age of Trilobites

Cambrian Period 550-505 mya Complex organisms became gradually more common in the millions of years immediately preceding the Cambrian, but it wasn't until this period that mineralized - hence readily fossilized - organisms became common. Most of the continents resembled deserts spanning from horizon to horizon. Stromatolites The diversification of lifeforms was relatively rapid during this period, and is termed the Cambrian explosion.

Ordovician Period 505-438 mya First starfish, sea urchins, blastoids, eurypterids, bryozoa, scaphopods, jawless fish, echinoids. The Age of Cephalopods

Silurian Period 438-408 mya An eurypterid, a prehistoric sea scorpion First land plants, ferns, sharks, boney fish, water scorpions. The Age of Coral

Devonian Period 408-360 mya Early tetrapods Acanthostega (foreground) and Ichthyostega. First insects, tetrapods, ammonites, placoderms. The Age of Fishes

Carboniferous Period Mississippian Epoch 360-325 mya Crinoid meadow in a shallow sea The Age of Crinoids First reptiles, spiders, amphibians. Why is it called the Carboniferous Period? Hint: There was no fungi to decompose the dead trees.

Carboniferous Period Pennsylvanian Epoch 325-286 mya First conifers, synapsids The Age of Plants and Giant Insects Dragonfly: 75 centimeter wingspan

Permian Period 286-248 mya Heyday of synapsids, including pelycosaurs The Age of Amphibians Early

Permian Extinction 248-251 mya The Permian–Triassic (P–Tr) extinction event, informally known as the Great Dying, was an extinction event that occurred about 250 million years ago, forming the boundary between the Permian and Triassic geologic periods.

Permian Extinction 248-251 mya It was the Earth's most severe extinction event, with up to 96 percent of all marine species and 70 percent of terrestrial vertebrate species becoming extinct; it is the only known mass extinction of insects. 57% of all families and 83% of all genera were killed off. Because so much biodiversity was lost, the recovery of life on earth took significantly longer (10 to 50 million years) than after other extinction events. This event has been described as the "mother of all mass extinctions".

Permian Extinction 248-251 mya There are several proposed mechanisms for the extinctions; An earlier peak was likely due to gradualistic environmental change such as sea-level change, anoxia, increasing aridity, and a shift in ocean circulation driven by climate change. The later peak was probably due to a catastrophic event(s) such as impact events, increased volcanism, or sudden release of methane hydrates from the sea floor

Triassic Period 248-213 mya First turtles, cycads, lizards, dinosaurs, mammals The Age of Dinosaurs (1)

Jurassic Period 213-145 mya First squids, frogs, birds, salamanders The Age of Dinosaurs (2)

Cretaceous Period 145-65 mya The Age of Dinosaurs (3) First flowering plants, snakes, modern fish, rise and fall of toothed birds, heyday of dinosaurs

The K-T Extinction 65.5 mya The Cretaceous–Tertiary extinction event was a large-scale mass extinction of animal and plant species in a geologically short period of time. Widely known as the K–T extinction event, it is associated with a geological signature known as the K–T boundary, usually a thin band of sedimentation found in various parts of the world.

The K-T Extinction 65.5 mya Scientists theorize that the K–T extinctions were caused by one or more catastrophic events, such as massive asteroid impacts (like the Chicxulub impact), or increased volcanic activity. 85% of all species died in the K-T extinction.

The K-T Extinction 65.5 mya

Iridium is extremely rare in normal rock but common in asteroids. The K-T Extinction 65.5 mya Several impact craters and massive volcanic activity, such as that in the Deccan traps, have been dated to the approximate time of the extinction event. These geological events may have reduced sunlight and hindered photosynthesis, leading to a massive disruption in Earth's ecology. K-T boundary layer Iridium is extremely rare in normal rock but common in asteroids.

Tertiary Period 65-1.8 mya Diversification of mammals, first marine and large terrestrial animals, horses, whales, monkeys, first grasses, apes, anthropoids, first hominids. The Age of Mammals

Quaternary Period 1.8 mya to present Mammoths, mastodons, Neanderthals, first modern human beings (Homo sapiens) The Age of Mammals