3 Every Rock Tells a Story…. All rocks that we have on earth today are made up of all the same stuff as the rocks that dinosaurs walked, crawled, or swam over.While the stuff that rocks are made of has stayed the same, the rocks themselves, have not.Over time rocks are recycled into new rocksQUESTIONS???What are some modern uses of rocks?How does a rock form?
4 When classifying a rock sample geologists observe the rock’s color and texture and determine its mineral composition. These observations help identify what type of rock it is.Texture: the size, shape, and pattern of the rock’s grain.Color: the apparent color of the rock, on the inside and the outside.Mineral composition: The minerals that make up the different parts of a rock.
7 What are the 3 major rock types and how can they change from one type to another type?
8 Rocks are classified by how they formed and what they’re made of Rocks are classified by how they formed and what they’re made of. There are 3 general classes of rocks:Igneous RocksMetamorphic RocksSedimentary Rocks
9 Igneous means “born of fire” Igneous RocksIgneous means “born of fire”
11 How is lava different from magma? Igneous RocksIgneous Rocks… are formed when lava and magma crystallize to form solid rock.QUESTION???How is lava different from magma?
12 Magma vs. LavaAll igneous rocks differ from one another in what they are made of and how fast they cooled.The longer it takes for the magma or lava to cool, the more time mineral crystals have to grow. The more time the crystals have to grow the coarser the texture of the resulting igneous rock.Magma is a hot liquid made of melted minerals. When magma pours onto the earth’s surface it is called lava.Igneous rock can form underground, where the magma cools slowly. Or, igneous rock can form above ground, where the magma cools quickly.The crystals grow together and form one igneous rock.
14 Big Bend National Park, Texas. Three Dike HillBig Bend National Park, Texas.
15 3 Ways a Rock Can MeltTemperature – An increase in temperature deep within the Earth’s crust can cause the minerals in a rock to melt.Pressure – The high pressure deep within the Earth forces minerals melt from intense heat and pressure.Composition – Fluids like water and carbon dioxide enter a rock that is close to its melting point. When these fluids combine with the rock, they can lower the melting point of the rock enough for it to melt and form magma.
16 2 Types of Igneous RocksINTRUSIVE IGNEOUS ROCKS – When igneous rocks are formed by magma that cools BENEATH Earth’s surface, they are called intrusive igneous rocksEXTUSIVE IGNEOUS ROCKS – When igneous rocks are formed by LAVA ON Earth’s surface, they are called extrusive igneous rocks
17 INTRUSIVE IGNEOUS ROCK Enchanted Rock, near Llano, TX is exposed intrusive formation made of granite.
18 EXTRUSIVE IGNEOUS ROCK Extrusive rock cools quickly on the surface and contains either very small crystals or none at all.
19 Example of Igneous Rock Lava flowFort Davis State Park, Texas
20 Into the BedrockOn top (Exit)Intrusive (has crystals)Extrusive (no crystals)
22 Sedimentary Rocks QUESTION??? Sedimentary Rocks…are formed when sediments (sand clay, and silt) are compressed and become solid rockQUESTION???Can you name the 4 ways Sedimentary Rock can be formed?
23 Formation of Sedimentary Rocks ErosionDepositionCompactionCementation
24 Example of Sedimentary Rock Each layer takes approximately10,000 years to make.
25 The process by which sediment becomes sedimentary rock LithificationThe process by which sediment becomes sedimentary rock1st step : Erosion2nd step : Deposition3rd step : Compaction4th step : CementationElephant Rock near Big Bend National Park, Texas
26 Sedimentary Rocks : Erosion Destructive forces are constantly breaking up and wearing away all the rocks on Earth’s surfaceThe forces include heat and cold, rain, waves, and grinding iceErosion occurs when running water or wind loosens and carry away the fragments of rock.Santa Elena CanyonBig Bend National Park
28 Sedimentary Rocks: Deposition Deposition is the process by which sediment settles out of the water or wind carrying it.Moving water or wind slows and deposits the sediment.Sediment may include shells, bones, leaves, stems, and other remains of living things.After sediment has been deposited, the processes of compaction and cementation change the sediment into sedimentary rock.Remains of living things in the sediment may slowly harden and change into fossils trapped in the rock.Overlook at La CuestaBig Bend Ranch State Park
29 Alluvial Fan near Madera Canyon Big Bend Ranch State Park
30 Sedimentary Rocks: Compaction New sediments fit together loosely, but gradually, thick layers of sediment build up creating new layers.These layers are heavy and press down on the layers beneath them.Compaction is the process that presses sediments together.Weight of the layers compacts the sediments, squeezing them tightly together.The layers often remain visible in the sedimentary rock.Rock Formation in Ernst Tinaja CanyonBig Bend National Park
31 Sedimentary Rocks: Cementation Cementation is the process in which dissolved minerals crystallize and glue particles of sediment together.While compaction is taking place, the minerals in the rock slowly dissolve in the water.The dissolved minerals seep into the spaces between particles of sediment.It takes millions of years for compaction and cementation to transform loose sediments into solid sedimentary rock.
32 Sedimentary Transformations Point A: Water or wind deposits sediments (Deposition)Point B: The heavy sediments press down on the layers beneath (Compaction)Point C: Dissolved minerals flow between the particles and cement them together (Cementation)
34 Metamorphic Rocks QUESTION??? Metamorphic Rocks…are formed when an existing rock is partially melted, squeezed, or bothQUESTION???What rock type does metamorphic rocks come from?
35 Metamorphic rocks are rocks that have "morphed" into another kind of rock. These rocks were once igneous or sedimentary rocks.
36 How do sedimentary and igneous rocks change? The rocks are under tons and tons of pressure, which fosters heat build up, and this causes them to change.If you exam metamorphic rock samples closely, you'll discover how flattened some of the grains in the rock are.
37 REVIEWGeologists classify rocks by observing color, texture and mineral composition.There are 3 general classes of rocks: Igneous, Sedimentary, and Metamorphic.
38 Igneous RocksIgneous Rocks… are formed when lava and magma crystallize to form solid rock.There are 2 forms of Igneous RocksIntrusiveExtrusive
39 Sedimentary RocksSedimentary Rocks…are formed when sediments (sand clay, and silt) are compressed and become solid rockSedimentary Rocks can be formed in 4 ways:ErosionDepositionCompactionCementation
40 Metamorphic RocksMetamorphic Rocks…are formed when an existing rock is partially melted, squeezed, or bothMetamorphic rocks are formed from Igneous and Sedimentary rocks under extreme:HeatPressure