What is a Ro c k?  Naturally-occurring mixtures of minerals, mineraloids (no crystals), or organic matter Types of Rocks…  The three main kinds of rock are igneous, sedimentary and metamorphic rock – Igneous rock: forms when magma/lava cools and hardens – Sedimentary rock: forms when sediments are buried, compacted & cemented together – Metamorphic rock: forms when existing rock is subjected to great heat & pressure over a long period of time What is the diffe re nc e be twe e n a ro c k and a mine ral?  Rocks are made up of ONE or MORE minerals Onc e a ro c k is fo rme d, e s it s tay the s ame ro c k fo re ve r?  NO!  Rocks are continually changed by many processes, such as weathering, erosion, compaction, cementation, melting, and cooling  Rocks can change to and from the three types What is the pro c e s s thro ug h whic h ro c ks c hang e ?  The Rock Cycle—earth materials change back and forth among the different types of rocks  No set path a rock takes to become another kind of rock Question Lava Magma reaches the surface flows from a volcano as Check Answer Question Intrusive Magma trapped below the surface forms large – grained rock when it cools Check Answer Question Extrusive Magma cooling at or near Earth’s surface forms small-grained igneous rock Check Answer Question Intrusive and extrusive Igneous rocks are classified in ways Check Answer Question 10 cool Volcanic glass rock so quickly that few crystals form Check Answer Question 11 Heat and pressure _ and result from one layer of rock on top of another layer Check Answer Question 12 magma Sometime temperature and pressure are great enough to melt rock, forming Check Answer Question 13 Foliated texture _ texture – mineral grains flatten and line up in parallel layers or bands Check Answer Question 14 Nonfoliated texture _ texture - mineral grains grow and rearrange but not form layers Check Answer Question 15 Pressure Sometimes flattens mineral grains in rocks without melting them Check Answer Question 16 Sedimentary Rock Type of rock mostly found on the exposed surface of Earth Check Answer Question 17 layers Sedimentary Rocks form in Check Answer Question 18 sediments Rock fragments, mineral grains, and bits of plants and animal remains moved by wind, water, ice or gravity are called _ Check Answer Question 19 cementation When water and other minerals move through open spaced between larger sediments, gluing them together, occurs Check Answer Question 20 Organic sedimentary _ _ rocks are made from the remains of once – living plants or animals Check Answer [...]... Detrial)—made of broken pieces of other rocks Formed when rock fragments are squeezed together Clastic-Sedimentary Rocks Shale: Formed from tiny particles of clay compacted together  Sandstone: Forms from the compaction and cementation of small particles of sand  Clastic-Sedimentary Rocks   Conglomerate: Formed from fragments of various sizes of rocks and pebbles Fragments are rounded because they have... igneous rock)  Usually have SMALL or NO crystals (they cooled too quickly) Granite: Intrusive or Extrusive? Why? Obsidian: Intrusive or Extrusive? Why? COMPOS ITION— What kind of substances or minerals are rocks made of Basaltic Igneous Rocks —made from lava/magma that is low in silica, rich in iron and magnesium Rocks are darkcolored Granitic Igneous Rocks—made from magma/lava high in silica and oxygen... ice or gravity then deposited into layers  Sedimentary rocks represent 7% of the Earth’s crust, but they cover 70% of the Earth’s surface  Sedimentary rocks are fossil-carrying rocks What turns sediments into solid rock?  Water or wind breaks down and deposits sediment (erosion & deposition)  Elements of Erosion are heat, cold, rain, waves, and grinding ice  At first sediments fit together loosely,...  The core, mantle, & crust are one giant rock recycling machine  “Ignis” = Latin for “fire”  Formed from the cooling of either magma or lava  The most abundant type of rock  Classified according to their origin and composition  Igneous Rocks come from magma/lava cooling down ORIGIN— Where rocks are formed  Below ground = from magma (intrusive igneous rock)  Usually have LARGE crystal grains... particles and cement them together (cementation) How can sedimentary layers help us understand the age of fossils? As sedimentary rocks are deposited, they form horizontal layers  Scientists know that the layers on top (and the fossils in the top layer) are YOUNGER than the fossils in lower layers  3 Type s o f S e dime ntary Ro c ks :  Clastic (also called Detrial)—made of broken pieces of other rocks... iron and magnesium Rocks are darkcolored Granitic Igneous Rocks—made from magma/lava high in silica and oxygen Rocks are lightcolored Andesitic Igneous Rocks— have a composition between basaltic and granitic Diorite-has course grains Basalt-no course grains Granite  Formed from sediments (rock fragments, mineral grains, animal & plant remains-shells, bones, leaves, stems) that are pressed or cemented... with sharp edges Formed from various size of rocks and pebbles 3 Type s o f S e dime ntary Ro c ks : Organic—remains of plants and animals are deposited in thick layers  Organic refers to substances that once were part of living things or were made by living things which contain calcite or calcium carbonate (Can be tested by using acid) Organic-Sedimentary Rocks   Coal: Remains of swamp plants buried...   Coal: Remains of swamp plants buried in water or by volcanic ash Limestone: Formed by hard shells of once living things such as coral, clams, oysters, and snails When they die their shells pile up and are covered by other sediments compacting and cementing them