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In geology, a rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition and the way in which it is formed. Rocks form the Earth's outer solid layer, the crust, and most of its interior, except for the liquid outer core and pockets of magma in the asthenosphere.

Rocks are usually grouped into three main groups: igneous rocks, sedimentary rocks and metamorphic rocks. Igneous rocks are formed when magma cools in the Earth's crust, or lava cools on the ground surface or the seabed. Sedimentary rocks are formed by diagenesis or lithification of sediments, which in turn are formed by the weathering, transport, and deposition of existing rocks. Metamorphic rocks are formed when existing rocks are subjected to such high pressures and temperatures that they are transformed—something that occurs, for example, when continental plates collide.

The scientific study of the character and origin of rocks is called petrology, which is an essential subdiscipline of geology. Most rocks contain silicate minerals, compounds that include silica tetrahedra in their crystal lattice, and account for about one-third of all known mineral species and about 95% of the earth's crust. The proportion of silica in rocks and minerals is a major factor in determining their names and properties. Rock outcrop along a mountain creek near Orosí, Costa Rica.

Rocks are classified according to characteristics such as mineral and chemical composition, permeability, texture of the constituent particles, and particle size. These physical properties are the result of the processes that formed the rocks. Over the course of time, rocks can be transformed from one type into another, as described by a geological model called the rock cycle. This transformation produces three general classes of rock: igneous, sedimentary and metamorphic.

Those three classes are subdivided into many groups. There are, however, no hard-and-fast boundaries between allied rocks. By increase or decrease in the proportions of their minerals, they pass through gradations from one to the other; the distinctive structures of one kind of rock may thus be traced, gradually merging into those of another. Hence the definitions adopted in rock names simply correspond to selected points in a continuously graduated series.

Rock 

Italy officially the Italian Republic or Republic of Italy is a country consisting of a peninsula delimited by the Alps and several islands surrounding it, whose territory largely coincides with the homonymous geographical region. Italy is located in the middle of the Mediterranean Sea, in Southern Europe it is also considered part of Western Europe. A unitary parliamentary republic with Rome as its capital and largest city, the country covers a total area of 301,230 km2 (116,310 sq mi) and shares land borders with France, Switzerland, Austria, Slovenia, as well as the enclaved microstates of Vatican City and San Marino. Italy has a territorial exclave in Switzerland, Campione. With over 60 million inhabitants, Italy is the third-most populous member state of the European Union.

Due to its central geographic location in Southern Europe and the Mediterranean, Italy has historically been home to myriad peoples and cultures. In addition to the various ancient peoples dispersed throughout what is now modern-day Italy, the most predominant being the Indo-European Italic peoples who gave the peninsula its name, beginning from the classical era, Phoenicians and Carthaginians founded colonies mostly in insular Italy, Greeks established settlements in the so-called Magna Graecia of Southern Italy, while Etruscans and Celts inhabited central and northern Italy respectively. An Italic tribe known as the Latins formed the Roman Kingdom in the 8th century BC, which eventually became a republic with a government of the Senate and the People. The Roman Republic initially conquered and assimilated its neighbours on the Italian peninsula, eventually expanding and conquering parts of Europe, North Africa and Asia. By the first century BC, the Roman Empire emerged as the dominant power in the Mediterranean Basin and became a leading cultural, political and religious centre, inaugurating the Pax Romana, a period of more than 200 years during which Italy's law, technology, economy, art, and literature developed.

Italy has an advanced economy. The country is the ninth-largest by nominal GDP (third in the European Union), the eighth-largest by national wealth and the third-largest by central bank gold reserve. It ranks highly in life expectancy, quality of life healthcare and education. The country is a great power and it has a significant role in regional and global economic, military, cultural, and diplomatic affairs.


Italy

A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' Food and Agriculture Organization (FAO) defines a forest as, "Land spanning more than 0.5 hectares with trees higher than 5 meters and a canopy cover of more than 10 percent, or trees able to reach these thresholds in situ. It does not include land that is predominantly under agricultural or urban use." Using this definition, Global Forest Resources Assessment 2020 (FRA 2020) found that forests covered 4.06 billion hectares (10.0 billion acres; 40.6 million square kilometres; 15.7 million square miles), or approximately 31 percent of the world's land area in 2020.

Forests are the predominant terrestrial ecosystem of Earth, and are distributed around the globe. More than half of the world's forests are found in only five countries (Brazil, Canada, China, the Russian Federation, and the United States of America). The largest share of forests (45 percent) are in the tropical latitudes, followed by those in the boreal, temperate, and subtropic domains.

Forests account for 75% of the gross primary production of the Earth's biosphere, and contain 80% of the Earth's plant biomass. Net primary production is estimated at 21.9 gigatonnes of biomass per year for tropical forests, 8.1 for temperate forests, and 2.6 for boreal forests.

Forests at different latitudes and elevations, and with different precipitation and evapotranspiration form distinctly different biomes: boreal forests around the North Pole, tropical moist forests and tropical dry forests around the Equator, and temperate forests at the middle latitudes. Areas at higher elevations tend to support forests similar to those at higher latitudes, and the amount of precipitation also affects forest composition.

Almost half the forest area (49 percent) is relatively intact, while 9 percent is found in fragments with little or no connectivity. Roughly 80 percent of the world's forest area is found in patches larger than 1 million hectares (2.5 million acres). The remaining 20 percent is located in more than 34 million patches around the world – the vast majority less than 1,000 hectares (2,500 acres) in size.

Forest

A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. A mountain differs from a plateau in having a limited summit area, and is larger than a hill, typically rising at least 300 metres (1000 feet) above the surrounding land. A few mountains are isolated summits, but most occur in mountain ranges.

Mountains are formed through tectonic forces, erosion, or volcanism, which act on time scales of up to tens of millions of years. Once mountain building ceases, mountains are slowly leveled through the action of weathering, through slumping and other forms of mass wasting, as well as through erosion by rivers and glaciers.

High elevations on mountains produce colder climates than at sea level at similar latitude. Because of the less hospitable terrain and climate, mountains tend to be used less for agriculture and more for resource extraction, such as mining and logging, along with recreation, such as mountain climbing and skiing.

The highest mountain on Earth is Mount Everest in the Himalayas of Asia, whose summit is 8,850 m (29,035 ft) above mean sea level. The highest known mountain on any planet in the Solar System is Olympus Mons on Mars at 21,171 m (69,459 ft).

There are three main types of mountains: volcanic, fold, and block. All three types are formed from plate tectonics: when portions of the Earth's crust move, crumple, and dive. Compressional forces, isostatic uplift and intrusion of igneous matter forces surface rock upward, creating a landform higher than the surrounding features. Major mountains tend to occur in long linear arcs, indicating tectonic plate boundaries and activity.

Climate in the mountains becomes colder at high elevations, due to an interaction between radiation and convection. The ground then heats the air at the surface. If radiation were the only way to transfer heat from the ground to space, the greenhouse effect of gases in the atmosphere would keep the ground at roughly 333 K (60 °C; 140 °F), and the temperature would decay exponentially with height. However, when air is hot, it tends to expand, which lowers its density. Thus, hot air tends to rise and transfer heat upward.

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