How do minerals form? Notes: 3/13/09

How do mineral crystals form? A. Rivers carrying sediment deposits it somewhere B. Water evaporates leaving behind minerals that were dissolved C. Molten rock cools and crystallizes. D. All of the above E. B and C only

Crystallization of Melted Minerals The closer to the surface, the faster the magma cools Slow cooling (1000s of years) Fast cooling (The minerals get hard before the atoms have time to get into crystal shapes)

Crystallization of Minerals Dissolved in Water Hot water solutions in the earth cool and minerals form Example: metals found in veins Evaporating water can leave behind crystals Example: sea water leaving potassium crystals

Types of Minerals Silicates Contain a mixture of oxygen and silicon make up 75-90% of earth’s crust Nonsilicates NOT formed from oxygen and silicon Combinations of oxygen, iron, carbon, and sulfur

3.2 Igneous Rocks As molten rock cools, minerals crystallize and form igneous rocks. Extrusive igneous rocks cool quickly at Earth's surface. Intrusive igneous rocks cool slowly within Earth.

What type of igneous rock has larger mineral crystals? A. Intrusive, because it cools more slowly B. Extrusive, because it cools more quickly C. Volcanic, because of the gas present D. Sediment, because there’s more layers

IntrusiveExtrusive Cools in the earth more slowly Larger Mineral Crystals Examples: granite and gabbro When surface rock wears away, intrusive rock can surface; it is harder and lasts longer Cools on earth’s surface quickly Small mineral crystals or none at all Examples: scoria, pumice, obsidian Low silica = flows easy; volcanoes with gently sloping sides (Hawaiian islands) High silica = cone shaped volcanoes with steep sides

The color igneous rocks is determined by how much silica is in it. A. Yes B. No

Composition of Igneous Rocks Most are made of silicates High in silicates = light color Low levels of silicates = dark color

As a rock gets buried deeper in the earth, which of the following does NOT happen? A. It can get melted into magma. B. It can turn into sediment. C. It can start the process of foliation. D. More mica can start to form.

Why do rocks change as they get buried deeper? Increased heat Increased pressure

heat and pressure 3.4 Metamorphic rocks form as existing rocks change. Metamorphic rocks form as the structure of the parent rocks change and as their minerals recrystallize. shale schist recrystallization foliation The process by which bonds between atoms in minerals break and re-form in new ways during metamorphism. The arrangement of minerals within rocks into flat or wavy parallel bands; a characteristic of most metamorphic rocks.

What is the third type of rock called? Main PROCESS that makes sedimentary rock… “WETDC” Weathering Erosion Transportation Deposition Cementation SEDIMENTARY

What is true about limestone? A. It is made from water evaporating. B. It is made from shells. C. It only forms in the desert.

3.3 Sedimentary rocks form from earlier rocks. sediment Layers of sedimentary rocks form as sediments are pressed or cemented together dissolved minerals re-form as water evaporates Limestone: forms when shells are cemented together and some of the minerals dissolve and reform. (reacts with acid because of the calcite) Fossils: are found only in sedimentary rocks

Where would a conglomorate sedimentary rock most likely be formed? A. Where a river is moving rapidly. B. Where a river is moving slowly. C. In the ocean.

Different types of sedimentary rocks form because of the speed of the water.