Geology ( Rocks )

THE STRUCTURE OF THE EARTH CRUST

The majority of research in geology is associated with the study of rock, as rock provides the primary record of the majority of the geologic history of the Earth. There are three major types of rock: igneous, sedimentary, and metamorphic. The rock cycle is an important concept in geology which illustrates the relationships between these three types of rock, and magma. When a rock crystallizes from melt (magma and/or lava), it is an igneous rock. Igneous rock can be weathered and eroded, and then redeposited and lithified into a sedimentary rock, or be turned into a metamorphic rock due to heat and pressure that change the mineral content of the rock which gives it a characteristic fabric. The sedimentary rock can then be subsequently turned into a metamorphic rock due to heat and pressure and is then weathered, eroded, deposited, and lithified, ultimately becoming a sedimentary rock. Sedimentary rock may also be re-eroded and redeposited, and metamorphic rock may also undergo additional metamorphism. All three types of rocks may be re-melted; when this happens, a new magma is formed, from which an igneous rock may once again crystallize.MineralsTo study these three types of rocks, geologists evaluate the minerals that make up the rock. All the colors you see in rocks are the different minerals crystallized within. Each mineral has distinct physical properties and there are multiple tests that a geologist can do to determine each one. The Mineral Identification tests are:

• Luster: Measurement of the amount of light reflected from the surface. Luster is broken up into Metallic and Non-metallic.

• Color: Minerals are grouped by their color. Mostly diagnostic but impurities can change a mineral’s color.

• Streak: Performed by taking a porcelain plate and scratching the mineral on it. The color of the streak can help you name the mineral.

• Hardness: The resistance of a mineral to scratch.

• Breakage Pattern: A mineral can either show fracture or cleavage. Fracture being breakage of uneven surfaces and cleavage being breakage along closely spaced parallel planes.

• Specific Gravity: the weight of a specific volume of a mineral.

• Effervescence: Involves dripping HCL on a mineral to test for fizzing.

• Magnetism: Involves using a magnet to test for magnetism.

• Taste: Minerals can have a distinctive taste like Halite (tastes like salt).

• Smell: Minerals can have a distinctive odor. For example, sulfur smells like rotten egg

Geology (from the Ancient Greek γῆ, gē, i.e. "earth" and -λoγία, -logia, i.e. "study of, discourse"^[1][2]) is an earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can also refer generally to the study of the solid features of any terrestrial planet (such as the geology of the Moon or Mars).Geology gives insight into the history of the Earth by providing the primary evidence for plate tectonics, the evolutionary history of life, and past climates. Geology is important for mineral and hydrocarbon exploration and exploitation, evaluating water resources, understanding of natural hazards, the remediation of environmental problems, and for providing insights into past climate change. Geology also plays a role in geotechnical engineering and is a major academic discipline.

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Skeleton and model of a dodo

Dodo as a extinct animal

The dodo (Raphus cucullatus) is an extinct flightless bird that was endemic to the island of Mauritius, east of Madagascar in the Indian Ocean. The dodo's closest genetic relative was the also extinct Rodrigues solitaire, the two forming the subfamily Raphinae of the family of pigeons and doves. The closest living relative of the dodo is the Nicobar pigeon. A white dodo was once thought to have existed on the nearby island of Réunion, but this is now thought to have been confusion based on the Réunion ibis and paintings of white dodos.

Subfossil remains show the dodo was about 1 metre (3 ft 3 in) tall and may have weighed 10.6–21.1 kg (23–47 lb). The dodo's appearance in life is evidenced only by drawings, paintings, and written accounts from the 17th century. Because these vary considerably, and because only some illustrations are known to have been drawn from live specimens, its exact appearance in life remains unresolved, and little is known about its behaviour. Though the dodo has historically been considered fat and clumsy, it is now thought to have been well-adapted for its ecosystem. It has been depicted with brownish-grey plumage, yellow feet, a tuft of tail feathers, a grey, naked head, and a black, yellow, and green beak. It used gizzard stones to help digest its food, which is thought to have included fruits, and its main habitat is believed to have been the woods in the drier coastal areas of Mauritius. One account states its clutch consisted of a single egg. It is presumed that the dodo became flightless because of the ready availability of abundant food sources and a relative absence of predators on Mauritius.

The first recorded mention of the dodo was by Dutch sailors in 1598. In the following years, the bird was hunted by sailors and invasive species, while its habitat was being destroyed. The last widely accepted sighting of a dodo was in 1662. Its extinction was not immediately noticed, and some considered it to be a mythical creature. In the 19th century, research was conducted on a small quantity of remains of four specimens that had been brought to Europe in the early 17th century. Among these is a dried head, the only soft tissue of the dodo that remains today. Since then, a large amount of subfossil material has been collected on Mauritius, mostly from the Mare aux Songes swamp. The extinction of the dodo within less than a century of its discovery called attention to the previously unrecognised problem of human involvement in the disappearance of entire species. The dodo achieved widespread recognition from its role in the story of Alice's Adventures in Wonderland, and it has since become a fixture in popular culture, often as a symbol of extinction and obsolescence.

Definition of Reptiles as an animal

Reptiles are tetrapod (four-limbed vertebrate) animals in the class Reptilia, comprising today's turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives. The study of these traditional reptile orders, historically combined with that of modern amphibians, is called herpetology.

Because some reptiles are more closely related to birds than they are to other reptiles (e.g., crocodiles are more closely related to birds than they are to lizards), the traditional groups of "reptiles" listed above do not together constitute a monophyletic grouping (or clade). For this reason, many modern scientists prefer to consider the birds part of Reptilia as well, thereby making Reptilia a monophyletic class.^[1][2][3][4]

The earliest known proto-reptiles originated around 312 million years ago during the Carboniferous period, having evolved from advanced reptiliomorph tetrapods that became increasingly adapted to life on dry land. Some early examples include the lizard-like Hylonomus and Casineria. In addition to the living reptiles, there are many diverse groups that are now extinct, in some cases due to mass extinction events. In particular, the K–Pg extinction wiped out the pterosaurs, plesiosaurs, ornithischians, and sauropods, as well as many species of theropods (e.g. Tyrannosaurus, Velociraptor, Spinosaurus, Allosaurus and birds), crocodyliforms, and squamates (e.g. mosasaurids).

Modern non-avian reptiles inhabit every continent with the exception of Antarctica. (If birds are classed as reptiles, then all continents are inhabited.) Several living subgroups are recognized: Testudines (turtles and tortoises), approximately 400 species;^[5] Sphenodontia (tuatara from New Zealand), 1 species;^[5][6] Squamata (lizards, snakes, and worm lizards), over 9,600 species;^[5] Crocodilia (crocodiles, gavials, caimans, and alligators), 25 species;^[5] and Aves (birds), 10,000 species.^[5]

Reptiles are tetrapod vertebrates, creatures that either have four limbs or, like snakes, are descended from four-limbed ancestors. Unlike amphibians, reptiles do not have an aquatic larval stage. Most reptiles are oviparous, although several species of squamates are viviparous, as were some extinct aquatic clades^[7] — the fetus develops within the mother, contained in a placenta rather than an eggshell. As amniotes, reptile eggs are surrounded by membranes for protection and transport, which adapt them to reproduction on dry land. Many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals, with some providing initial care for their hatchlings. Extant reptiles range in size from a tiny gecko, Sphaerodactylus ariasae, which can grow up to 17 mm (0.7 in) to the saltwater crocodile, Crocodylus porosus, which may reach 6 m (19.7 ft) in length and weigh over 1,000 kg (2,200 lb).

Spiders

Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other orders of organisms.^[2] Spiders are found worldwide on every continent except for Antarctica, and have become established in nearly every habitat with the exceptions of air and sea colonization. As of November 2015, at least 45,700 spider species, and 113 families have been recorded by taxonomists.^[1] However, there has been dissension within the scientific community as to how all these families should be classified, as evidenced by the over 20 different classifications that have been proposed since 1900.^[3]

Anatomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel. Unlike insects, spiders do not have antennae. In all except the most primitive group, the Mesothelae, spiders have the most centralized nervous systems of all arthropods, as all their ganglia are fused into one mass in the cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure.

Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of glands. Spider webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders. Spider-like arachnids with silk-producing spigots appeared in the Devonian period about 386 million years ago, but these animals apparently lacked spinnerets. True spiders have been found in Carboniferous rocks from 318 to 299 million years ago, and are very similar to the most primitive surviving suborder, the Mesothelae. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appeared in the Triassic period, before 200 million years ago.

A herbivorous species, Bagheera kiplingi, was described in 2008,^[4] but all other known species are predators, mostly preying on insects and on other spiders, although a few large species also take birds and lizards. It is estimated that 25 million tons of spiders kill 400–800 million tons of prey per year.^[5] Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Most detect prey mainly by sensing vibrations, but the active hunters have acute vision, and hunters of the genus Portia show signs of intelligence in their choice of tactics and ability to develop new ones. Spiders' guts are too narrow to take solids, and they liquefy their food by flooding it with digestive enzymes. They also grind food with the bases of their pedipalps, as arachnids do not have the mandibles that crustaceans and insects have.

Male spiders identify themselves by a variety of complex courtship rituals to avoid being eaten by the females. Males of most species survive a few matings, limited mainly by their short life spans. Females weave silk egg-cases, each of which may contain hundreds of eggs. Females of many species care for their young, for example by carrying them around or by sharing food with them. A minority of species are social, building communal webs that may house anywhere from a few to 50,000 individuals. Social behavior ranges from precarious toleration, as in the widow spiders, to co-operative hunting and food-sharing. Although most spiders live for at most two years, tarantulas and other mygalomorph spiders can live up to 25 years in captivity.

While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting pesticides. Spider silk provides a combination of lightness, strength and elasticity that is superior to that of synthetic materials, and spider silk genes have been inserted into mammals and plants to see if these can be used as silk factories. As a result of their wide range of behaviors, spiders have become common symbols in art and mythology symbolizing various combinations of patience, cruelty and creative powers. An abnormal fear of spiders is called arachnophobia.

DINOSAURS

Dinosaurs are a diverse group of reptiles of the clade Dinosauria that first appeared during the Triassic. Although the exact origin and timing of the evolution of dinosaurs is the subject of active research,^[1] the current scientific consensus places their origin between 231 and 243 million years ago.^[2] They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201 million years ago. Their dominance continued through the Jurassic and Cretaceous periods and ended when the Cretaceous–Paleogene extinction event led to the extinction of most dinosaur groups 66 million years ago.

Until the late 20th century, all groups of dinosaurs were believed to be extinct. The fossil record, however, indicates that birds, which are now termed "avian dinosaurs,"^[3] are the modern descendants of feathered dinosaurs,^[4] having evolved from theropod ancestors during the Jurassic Period.^[5] As such, birds were the only dinosaur lineage to survive the mass extinction event.^[6] Throughout the remainder of this article, the term "dinosaur" is sometimes used generically to refer to the combined group of avian dinosaurs (birds) and non-avian dinosaurs; at other times it is used to refer to the non-avian dinosaurs specifically, while the avian dinosaurs are sometimes simply referred to as "birds". This article deals primarily with non-avian dinosaurs.

Dinosaurs are a varied group of animals from taxonomic, morphological and ecological standpoints. Birds, at over 10,000 living species,^[7] are the most diverse group of vertebrates besides perciform fish.^[8] Using fossil evidence, paleontologists have identified over 500 distinct genera^[9] and more than 1,000 different species of non-avian dinosaurs.^[10] Dinosaurs are represented on every continent by both extant species (birds) and fossil remains.^[11] Through the first half of the 20th century, before birds were recognized to be dinosaurs, most of the scientific community believed dinosaurs to have been sluggish and cold-blooded. Most research conducted since the 1970s, however, has indicated that all dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction. Some are herbivorous, others carnivorous. Evidence suggests that egg laying and nest building are additional traits shared by all dinosaurs.

While dinosaurs were ancestrally bipedal, many extinct groups included quadrupedal species, and some were able to shift between these stances. Elaborate display structures such as horns or crests are common to all dinosaur groups, and some extinct groups developed skeletal modifications such as bony armor and spines. While the dinosaurs' modern-day surviving avian lineage (birds) are generally small due to the constraints of flight, many prehistoric dinosaurs (non-avian and avian) were large-bodied—the largest sauropod dinosaurs are estimated to have reached lengths of 39.7 meters (130 feet)^[12] and heights of 18 meters (59 feet)^[13] and were the largest land animals of all time. Still, the idea that non-avian dinosaurs were uniformly gigantic is a misconception based in part on preservation bias, as large, sturdy bones are more likely to last until they are fossilized. Many dinosaurs were quite small: Xixianykus, for example, was only about 50 cm (20 in) long.

Since the first dinosaur fossils were recognized in the early 19th century, mounted fossil dinosaur skeletons have been major attractions at museums around the world, and dinosaurs have become an enduring part of world culture. The large sizes of some dinosaur groups, as well as their seemingly monstrous and fantastic nature, have ensured dinosaurs' regular appearance in best-selling books and films, such as Jurassic Park. Persistent public enthusiasm for the animals has resulted in significant funding for dinosaur science, and new discoveries are regularly covered by the media.