THE GEOLOGICAL CYCLE
The earth is undergoing a constant, slow process of change, so slow by human standards that it is easy to gain the impression that everything is permanent and unalterable.
This diagram shows the way in which the bedrock 1 and mountains have emerged as a result of the crystallization of molten magma to form solid rock.
The upward folding of the mountain ranges 2 is also governed by plate tectonics, movements of segments of the earth’s crust and collisions between them.
In the course of time the bedrock is worn down 3 by weathering 4 , the effects of water and the atmosphere and gravitational forces, and the rocks are reduced to sand and clay
5 and eventually transported by water and wind into the seas. Here they are deposited on the sea bed 6 and harden 7 in time to form sedimentary rocks. Eventually 8 , as a result of movements in the earth’s crust, these sedimentary rocks are pressed down 9 further into the earth and melt 10 to form magma once more. All this forms a cycle of the matter of which the earth is composed that takes place over a period of hundreds of millions of years, although the processes that contribute to it are active all the time.
1 BEDROCK: Roques del fons / ciments.
2 MOUNTAIN RANGES: Serralades.
3 WEAR DOWN / WORN DOWN: Desgastar.
4 WEATHERING: Erosió.
5 CLAY: Argila.
6 SEA BED: Fons marí.
7 HARDEN: Endurir-se / soldificar.
8 EVENTUALLY: Finalment.
9 PRESS DOWN: Apretar.
10 MELT: Fundir-se / derretir-se.

The geologic cycle is a term used to describe the complex interactions between tectonic, hydrologic, rock, and biological sub-cycles. These various subcycles influence each other and may produce natural hazards 11 and processes important to environmental geology such as landslides 12 , earthquakes 13 , volcanic activity, flooding 14 , groundwater flow 15 , and weather.
The rock cycle is influenced by all the other geologic subcycles. For example, tectonic processes provide 16 the pressure and heat necessary to recrystalize some or all of the minerals in a rock and transform it from one rock type to another.
Internal geological processes are responsible for the formation of new rocks, the deformation of the materials of the crust and the formation of new ranges 17 and, therefore 18 , the formation of relief 19 .
The main geological processes involved in the internal cycle of the rocks and the formation of relief are: metamorphism, melting, solidification and the formation of mountain ranges
(orogeny).
 METAMORPHISM
Metamorphism is the solid-state recrystallization of pre-existing rocks due to 20 changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process.
There exist three types of metamorphism: contact, dynamic and regional.
 MELTING AND SOLIDIFICATION
When the pressure and temperature are high enough, there is a fusion of the rocks. This process takes place deep inside the crust and especially at the boundary 21 between the lithosphere and the asthenosphere.
11 HAZARD: Perill.
12 LANDSLIDES: Esllevissades.
13 EARTHQUAKES: Terratrèmols.
14 FLOODING: Inundacions.
15 GROUNDWATER FLOW: Fluxes d’aigua subterrània.
16 PROVIDE: Donar.
17 RANGES: Serralades.
18 THEREFORE: Per tant.
19 RELIEF: Relleu.
20 DUE TO: Degut a.
21 BOUNDARY: Frontera.

Melting involves the disappearance of the original structure of the rocks as well as a homogenization of materials with a new determined chemical composition. The resulting homogeneous melt is called magma.
The magma can be placed between existing solid rocks, through a process called intrusion . Intrusion triggers 22 the rising of magma through the crust which makes it to cool and finally solidificate. Solid magmas become igneous rocks 23 .
Devils Tower (WYOMING, USA) an igneous intrusion exposed when the surrounding softer rock eroded away.
 OROGENY
It refers to the process of mountain formation, especially by a folding 24 and faulting 25 of the earth's crust.
22 TRIGGER: Provoca.
23 ROQUES MAGMÀTIQUES.
24 FOLDING: Plec.
25 FAULTING: Falla.

a) How have the mountains in the diagram emerged? b) What are the factors that affect the wearing down of the bedrock? c) What are the two processes that affect the rocks? d) What happens to the rocks that are placed on the sea bed? e) Are geological processes static in time? f) What are the main geological processes involved in the formation of rocks and reliefs? g) What is magma?
a) Heat, pressure and chemical fluids are responsible for metamorphism. b) Melting occurs at the lithospere. c) In melting the original structure of the rocks is preserved. d) Igneous rocks are formed through the cooling and solidification of magma or lava. e) Igneous rock may form with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive (volcanic) rocks. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. f) Over 700 types of igneous rocks have been described, most of them having formed beneath the surface of Earth's crust. These have diverse properties, depending on their composition and how they were formed.
An intrusion is liquid rock that forms _______________(1) the surface of the
__________________(2). Magma from under the surface slowly moves its way up from deep within the earth and moves into any _____________(3) or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take ________________(4) of years or more to form. As the rock slowly __________________ (5) into a solid, the different

parts of the magma slowly crystallize into __________________(6). The more slowly the crystals form, the ________________(7) the crystals can get. Volcanic rock, by contrast, cools very _________________(8) on the surface of the earth, and thus, generally have only microscopic crystals, such as in an ____________________(9) cloud (whose crystals are tiny dust particles). Many mountain _________________(10), such as the Sierra Nevada in
California, are formed mostly by ____________________(11) rock, large granite (or related rock) formations.
Intrusions are one of two ways for igneous rock to form; the other way is ________________(12), that is, a volcano eruption or similar event. Technically speaking, an intrusion is any formation of intrusive igneous rock; rock formed from magma that cools and
_________________(13) within the crust of a planet . In contrast, an extrusion consists of extrusive rock; rock formed ___________________(14) the surface of the crust.