Geology: Earth: Overview

Last major division of geologic time lasting from 65 million years ago to the present. The Cenozoic is divided into the Tertiary (from 65 million years ago until 2 million years ago) and Quaternary (2 million years ago to the present) periods.

[Gr.,=middle life], major division of geologic time (see Geologic Timescale, table) from 65 to 225 million years ago. Great crustal disturbances that marked the close of the Paleozoic and the beginning of the Mesozoic eras brought about drastic changes in the topography of North America.

From The Columbia Encyclopedia
Paleozoic era (pā´´lēәzō´ĭk), a major division (era) of geologic time occurring between 570 to 240 million years ago. It is subdivided into six periods, the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.

Name of a major division of geologic time (see Geologic Timescale, table), from c.5 billion to 570 million years ago. It is now usually divided into the Archean and Proterozoic eons. Precambrian time includes 80% of the earth's history.

From Britannica concise encyclopedia
Older of the two divisions of Precambrian time. The Archean begins with the formation of the Earth's crust 4 billion years ago and extends to 2.5 billion years ago.

From Britannica concise encyclopedia
Younger of the two divisions of Precambrian time, from 2.5 billion to 542 million years ago.

The earliest geological period of the Palaeozoic era, lasting from c.590 to 505 million years ago.

Fifth period of the Paleozoic era of geologic time, from 350 to 290 million years ago.

The Cretaceous is the last period of the Mesozoic. It lasted for approximately 80 million years, ending 65 million years ago.

Fourth period of the Paleozoic era of geologic time between 408 and 360 million years ago.

A geological period of the Mesozoic era extending from c.213 to 144 million years ago.

The second of the geological periods of the Palaeozoic era, extending from c.505 to 438 million years ago.

A geological period of the Upper Palaeozoic era, extending from c.286 to 250 million years ago.

The third of the geological periods of the Palaeozoic era, extending from c.435 to 408 million years ago.

A period of geological time during the early Mesozoic era, lasting from about 240 to 200 million years ago.

Largest unit of landmasses on the earth. The continents include Eurasia (conventionally regarded as two continents, Europe and Asia), Africa, North America, South America, Australia, and Antarctica.

Arid region, usually partly covered by sand, having scanty vegetation or sometimes almost none, and capable of supporting only a limited and specially adapted animal population.

A plant community extending over a large area and dominated by trees, the crowns of which form an unbroken covering layer or canopy.

A piece of land, smaller than a continent, which is completely surrounded by water, eg Britain, Cyprus, Greenland, etc.

High land mass projecting conspicuously above its surroundings and usually of limited width at its summit.

Any of various vents in the Earth’s crust through which magma is or has previously been forced out onto the surface, forming various structures but usually taking the form of a conical hill due to the build up of solidified lava.

Moving mass of ice that survives year to year, formed by the compacting of snow into névé and then into granular ice and set in motion outward and downward by the force of gravity and the stress of its accumulated mass. Glaciers are usually found in high altitudes and latitudes.

A large area of still fresh or salt water, surrounded by land and lying in a depression in the Earth’s surface, which receives water from rivers, streams, springs, etc.

Interconnected mass of saltwater covering 70.78% of the surface of the earth, often called the world ocean.

Large body of water that flows down a slope along a channel restricted by adjacent banks and levees. A river starts at a point called its source, and enters a sea or lake at its mouth.

A stream that falls from a height. Waterfalls are often the sites of greatest concentration of energy dissipation along the course of a stream and have generally been regarded as forming where a soft rock is eroded from beneath a harder rock (the caprock model).

Trembling or shaking movement of the earth's surface.

General term for the processes by which the surface of the earth is constantly being worn away.

Moving mass of ice that survives year to year, formed by the compacting of snow into névé and then into granular ice and set in motion outward and downward by the force of gravity and the stress of its accumulated mass.

The warming of the Earth’s surface as a result of the trapping of long-wave radiation by carbon dioxide, ozone, and certain other gases in the Earth’s atmosphere.

Tropical cyclone in which winds attain speeds greater than 74 mi (119 km) per hr.

Precipitation in liquid form. It consists of drops of water falling from clouds; if the drops are very small, they are collectively termed drizzle.

Precipitation formed by the sublimation of water vapor into solid crystals at temperatures below freezing.

A violently destructive storm characterized by a funnel-shaped rotating column of air which can be seen extending downward from thunder clouds to the ground, tracing a narrow path across the land.

Series of catastrophic ocean waves generated by submarine movements, which may be caused by earthquakes, volcanic eruptions, landslides beneath the ocean, or an asteroid striking the earth. Tsunamis are also called seismic sea waves or, popularly, tidal waves.

Vents or fissures in the earth's crust through which gases, molten rock, or lava, and solid fragments are discharged.

Flow of air relative to the earth's surface. A wind is named according to the point of the compass from which it blows, e.g., a wind blowing from the north is a north wind.

Chemical compound of hydrogen and oxygen elements - H2O. It can exist as a solid (ice), liquid (water), or gas (water vapour).

Rock material occurring in the form of loose, rounded or angular grains, varying in size from .06 mm to 2 mm in diameter, the particles being smaller than those of gravel and larger than those of silt or clay.

Molten rock that erupts on the earth's surface, either on land or under the ocean, by a volcano or through a fissure.

Inorganic substance occurring in nature, having a characteristic and homogeneous chemical composition, definite physical properties, and, usually, a definite crystalline form.

Constituent of the Earth's crust composed of minerals or materials of organic origin that have consolidated into hard masses.

Antimony exists in two allotropic forms (see allotropy); the more common is silvery blue-white and has a rhombohedral crystalline structure.

Barium is a soft, silver-white, chemically active, poisonous metal with a face-centered cubic crystalline structure.

Beryllium is a strong, extremely light, high-melting, silver-gray metal with a close-packed hexagonal crystalline structure

Cobalt is one of the mineral elements known to be essential for health, but only required in minute amounts - a trace element.

Red-brown, very malleable and ductile, metallic element, atomic number 29, relative atomic mass 63.546.

Gold is very ductile and is the most malleable metal; it can be beaten into extremely thin sheets of gold leaf.

Lead (Pb) has been used since ancient times. It is commonly used in modern petroleum engineering, atomic reactors, and many organic (synthetic) compounds.

Lithium is a soft, silver-white metal.

Manganese is a pinkish-gray, chemically active metal.

General term for a large group of minerals, hydrous silicates of aluminum and potassium, often containing magnesium, ferrous iron, ferric iron, sodium, and lithium and more rarely containing barium, chromium, and fluorine.

Molybdenum is a hard, malleable, ductile, high-melting, silver-white metal with a body-centered cubic crystalline structure.

Nickel is a hard, malleable, ductile, lustrous, silver-white metal with a face-centered cubic crystalline structure.

Pure platinum is a malleable, ductile, lustrous, silver-white metal with a face-centered cubic crystalline structure.

The most abundant mineral, quartz is found in myriad colours, shapes, and varieties.

Pure silver is nearly white, lustrous, soft, very ductile, malleable, and an excellent conductor of heat and electricity.

Brittle, pale-yellow, non-metallic element, atomic number 16, relative atomic mass 32.064.

Tantalum is a rare, hard, blue-gray metal with a body-centered cubic crystalline structure. I

Tungsten is a very hard, silver-white to steel-gray metal with a body-centered cubic crystalline structure.

Hard, lustrous, silver-white, malleable and ductile, radioactive, metallic element of the actinide series, atomic number 92, relative atomic mass 238.029.

Vanadium is a soft, ductile, silver-grey metal.

Zinc is a lustrous bluish-white metal.

Fine-grained rock of volcanic origin, dark gray, dark green, brown, reddish, or black in color.

Colour: White, cream or grey, but often weathers brown or pinkish. Texture: Coarse, medium or fine; compact, sometimes earthy.

The so-called crust of the Earth is about 35 km thick under the continents but averages only some 7 km beneath the oceans. It is formed mainly of rocks of relatively low density.

Metamorphic rock composed wholly or in large part of calcite or dolomite crystals, the crystalline texture being the result of metamorphism of limestone by heat and pressure.

Rock altered in structure, composition, and texture by pressure or heat after its original formation.

Sediments are loose, unconsolidated rock particles and ions (i.e., charged atoms) dissolved in aqueous solutions. Sedimentary rocks, which constitute about 75% of all rocks exposed at the surface of the Earth, form when the particles are cemented together or when crystals precipitate from the solutions.