READ: Important Vocabulary Terms

READ: Important Vocabulary Terms

These are the most important vocabulary terms to learn this week. Please make sure you understand these terms. 

• A rock is a naturally formed, non-living Earth material. Rocks are made of minerals. 
  
• A mineral is a solid material that forms by a natural process. A mineral can be made of an element or a compound. It has a specific chemical composition. 
  
• Igneous rocks form when magma cools below Earth’s surface or lava cools at the surface.
  
• Sedimentary rocks form when sediments are compacted and cemented together.
  
• Sediments are pieces of rock. They may be gravel, sand, silt, or clay. 
  
• Metamorphic rocks form when an existing rock is changed by heat or pressure. The minerals in the rock change but do not melt.  
  
• The rock cycle depicts how the three major rock types – igneous, sedimentary, and metamorphic - convert from one to another.
  
• Erosion is when rock particles are moved by gravity, wind, water, or ice.  
  
• Sedimentation is when rock particles are deposited by gravity, wind, water, or ice. 
  
• Weathering wears rocks at the Earth’s surface down into smaller pieces. The small fragments are called sediments. 
  
• Metamorphism: When a rock is exposed to extreme heat and pressure within the Earth but does not melt, the rock becomes metamorphosed. Metamorphism may change the mineral composition and the texture of the rock. 
  
• Intrusive igneous rocks cool underground. Deep in the crust, magma cools slowly. Slow cooling gives crystals a chance to grow. Intrusive igneous rocks have relatively large crystals that are easy to see. 
  
• Extrusive igneous rocks form above the surface. The lava cools quickly as it pours out onto the surface. Extrusive igneous rocks cool much more rapidly than intrusive rocks. The rapid cooling time does not allow time for large crystals to form. So igneous extrusive rocks have smaller crystals than igneous intrusive rocks. 
  
• Mafic igneous rocks contain mafic minerals. Mafic minerals are dense and dark in color. They typically contain iron and magnesium; they are low in silica. 
  
• Felsic igneous rocks contain felsic minerals. They typically contain aluminum and sodium; they are high in silica. Quartz and potassium feldspar are felsic minerals. 
  
• Intermediate igneous rocks have a composition in between mafic and felsic.