Igneous Rocks - Cloze

First, do these activities: vocabulary. Listen to the recordings if necessary: MP3, MP3. Fill in all the gaps with the missing words, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Click the this button again for another letter. You can also click on "[?]" for a different hint. Note that you will lose points if you ask for hints or clues! Finally, do the quiz.

Primero, haz la actividad de vocabulario. Escucha la grabación si es necesario. Rellena los espacios en blanco con las palabras que faltan. Haz click en "Check" para comprobar tus aciertos. Si te resulta difícil la respuesta utiliza el botón "Hint" y te revelará una letra de la casilla en la que te encuentres, puedes clickear varias veces en "Hint" y te dará cada vez una letra más de la palabra. Para obtener ayuda también puedes clickear en el botón "[?]" y te dará una pista. Perderás puntos con las pistas.

Slow:     Fast:
   batholiths      beneath      coarse      cooling      cores      country      crust      crystallization      extrusive      flows      granite      igneous      intermingled      intrusive      magma      mantle      melts      metamorphic      naked      obsidian      pyroclastic      sedimentary      smokers      treacle      tuff      viscosity      viscous   
rock (derived from the Latin word igneus, meaning "of fire") is one of the three main rock types, the others being and rock.
Igneous rock is formed through the and solidification of or lava. Igneous rock may form with or without , either below the surface as (plutonic) rocks or on the surface as (volcanic) rocks. This magma can be derived from partial of pre-existing rocks in either a planet's or .
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. Over 700 types of igneous rocks have been described, most of them having formed the surface of Earth's crust. These have diverse properties, depending on their composition and how they were formed.
In terms of modes of occurrence, igneous rocks can be either (plutonic) or extrusive (volcanic):
Intrusive igneous rocks are formed from magma that cools and solidifies within the crust of a planet. Surrounded by pre-existing rock (called rock), the magma cools slowly, and as a result these rocks are grained. The mineral grains in such rocks can generally be identified with the eye. Intrusive rocks can also be classified according to the shape and size of the intrusive body and its relation to the other formations into which it intrudes. Typical intrusive formations are batholiths, stocks, laccoliths, sills and dikes.
The central of major mountain ranges consist of intrusive igneous rocks, usually . When exposed by erosion, these cores (called ) may occupy huge areas of the Earth's surface.

Extrusive igneous rocks are formed at the crust's surface as a result of the partial melting of rocks within the and crust. Extrusive Igneous rocks cool and solidify quicker than intrusive igneous rocks. Since the rocks cool very quickly, they are fine grained.
The melted rock, with or without suspended crystals and gas bubbles, is called . It rises because it is less dense than the rock from which it was created. When magma reaches the surface from beneath water or air, it is called lava. Eruptions of volcanoes into air are termed subaerial, whereas those occurring underneath the ocean are termed submarine. Black and mid-ocean ridge basalt are examples of submarine volcanic activity.

Magma which erupts from a volcano behaves according to its , determined by temperature, composition, and crystal content:
  • High-temperature magma, most of which is basaltic in composition, behaves in a manner similar to thick oil and, as it cools, . Long, thin basalt flows with pahoehoe surfaces are common.
  • Intermediate composition magma such as andesite tends to form cinder cones of ash, tuff and lava, and may have viscosity similar to thick, cold molasses or even rubber when erupted.
  • Felsic magma such as rhyolite is usually erupted at low temperature and is up to 10,000 times as as basalt. Volcanoes with rhyolitic magma commonly erupt explosively, and rhyolitic lava typically are of limited extent and have steep margins, because the magma is so viscous.
  • Felsic and intermediate magmas that erupt often do so violently, with explosions driven by release of dissolved gases — typically water but also carbon dioxide. Explosively erupted material is called tephra and includes tuff, agglomerate and ignimbrite. Fine volcanic ash is also erupted and forms ash deposits which can often cover vast areas.
    Because lava cools and crystallizes rapidly, it is fine grained. If the cooling has been so rapid as to prevent the formation of even small crystals after extrusion, the resulting rock may be mostly glass (such as the rock ). If the cooling of the lava happened slowly, the rocks would be coarse-grained.
    Because the minerals are mostly fine-grained, it is much more difficult to distinguish between the different types of extrusive igneous rocks than between different types of intrusive igneous rocks. Generally, the mineral constituents of fine-grained igneous rocks can only be determined by examination of thin sections of the rock under a microscope, so only an approximate classification can usually be made in the field.