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Time defined by Geology, Rocks and Minerals. Why rocks? Geology allows us to use rocks to see what the past was like on Earth Geology allows us to use.

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Presentation on theme: "Time defined by Geology, Rocks and Minerals. Why rocks? Geology allows us to use rocks to see what the past was like on Earth Geology allows us to use."— Presentation transcript:

1 Time defined by Geology, Rocks and Minerals

2 Why rocks? Geology allows us to use rocks to see what the past was like on Earth Geology allows us to use rocks to see what the past was like on Earth-environment -life forms -tectonic events -catastrophes

3 Geologic Time Scale Art by Ray Troll Art by Ray Troll Periods are defined by their MASS extinctions

4 Eras and New Mexico Precambrian- 9/10 ths of Earth’s History Precambrian- 9/10 ths of Earth’s History MYA MYA Where we are now started underwater, at the very end of this time period “New Mexico” surfaced. Where we are now started underwater, at the very end of this time period “New Mexico” surfaced. Granite and other metamorphic rocks formed during this time (Sandia Mt. and Sangre de Cristo) but because so long ago, much lost due to erosion. Granite and other metamorphic rocks formed during this time (Sandia Mt. and Sangre de Cristo) but because so long ago, much lost due to erosion.

5 Paleozoic MYA Fossils of trilobites come from, aquatic lifeforms, fish Fossils of trilobites come from, aquatic lifeforms, fish New Mexico was flooded with small seas, deposits of limestone and sandstone from those beaches and reefs that formed- Guadalupe Mts. New Mexico was flooded with small seas, deposits of limestone and sandstone from those beaches and reefs that formed- Guadalupe Mts. End of this era PANGEA forms, land becomes swampy End of this era PANGEA forms, land becomes swampy CARBONIFEROUS epoch- zooplankton and algae decompose to create modern petrol, coal CARBONIFEROUS epoch- zooplankton and algae decompose to create modern petrol, coal

6 Mesozoic MYA N M dries out again- leaves layered rock you see today- mesa and buttes N M dries out again- leaves layered rock you see today- mesa and buttes Environment a mix of swamps and deserts depending on where you are in state, on and off flooding of areas- shale, limestone, sandstone Environment a mix of swamps and deserts depending on where you are in state, on and off flooding of areas- shale, limestone, sandstone Era of dinosaurs- NM State Fossil- Coelophysis (Triassic) Era of dinosaurs- NM State Fossil- Coelophysis (Triassic) KT/ KPg Event- band in the rocks- SOMETHING caused a mass extinction which denotes the end of Mesozoic Era (asteroid(s)?) KT/ KPg Event- band in the rocks- SOMETHING caused a mass extinction which denotes the end of Mesozoic Era (asteroid(s)?)

7 Cenozoic 66 MYA to NOW! In NM, lots of volcanic activity- like the Valle Caldera- Redondo Peak- Lava Dome In NM, lots of volcanic activity- like the Valle Caldera- Redondo Peak- Lava Dome Volcanoes also formed Mogollan Mts, Datil Mts, Black Range, Sierra Blanca and Ship Rock- lots of igneous rocks Volcanoes also formed Mogollan Mts, Datil Mts, Black Range, Sierra Blanca and Ship Rock- lots of igneous rocks Albuquerque Volcano Field also formed during this time- Cinder cones Albuquerque Volcano Field also formed during this time- Cinder cones Anthropocene- possible rename for our epoch/ period Anthropocene- possible rename for our epoch/ period

8 How do we know the age of rocks? Look at the layers! Look at the layers! LAW OF SUPERPOSITION- the oldest rocks are at the bottom, the youngest are at the top LAW OF SUPERPOSITION- the oldest rocks are at the bottom, the youngest are at the top Nicholas Steno- Relative Stratigraphy 1669 Nicholas Steno- Relative Stratigraphy 1669 Evidence came in Rock dating using Radiometric Decay, looking at isotopes (ex U-235 decays to Pb- 207) - Date Igneous and Metamorphic only

9 Additional Evidence Carbon Dating viable organic remnants of life forms Carbon Dating viable organic remnants of life forms Cosmic Radiation- He-3 Cosmic Radiation- He-3 U-238, Zircon apatite has U- 238 as part of its crystalline structure U-238, Zircon apatite has U- 238 as part of its crystalline structure Paleomagnetism- Earth’s Magnetic field switches naturally Paleomagnetism- Earth’s Magnetic field switches naturally

10 Properties of Rock and Minerals

11 What is a mineral? Naturally occurring Naturally occurring Inorganic Inorganic Distinctive physical properties Distinctive physical properties Crystalline structure, consistent elemental composition/ atomic structure Crystalline structure, consistent elemental composition/ atomic structure

12 Mineral properties Color Color Luster Luster Habit (Shape) Habit (Shape) Cleavage & Fracture Cleavage & Fracture Streak Streak Hardness Hardness Other Other

13 Color: Not mineral specific

14 Luster: How minerals reflect light Non- metallic Metallic

15 Mineral Habit (Shape) Shape a mineral takes if grown unimpeded Mineral Java Applet Mineral Java Applet

16 Cleavage & Fracture Cleavage: planes of weakness along which minerals can break, weak areas of bonding- categorized by quality and difficulty Fracture: surfaces along which minerals can break, curved surface, irregular

17

18 Streak: The powdered form of a mineral

19 Hardness: Based on Moh’s scale of hardness

20 Other Properties Specific gravity Specific gravity Reaction to acid Reaction to acid Striations Striations Magnetism Magnetism Florescence Florescence

21 Ore- metal or mineral in its pure form that is economically useful Ore- metal or mineral in its pure form that is economically useful Alloy- solid mixture of 2 or more metals, created by smelting Alloy- solid mixture of 2 or more metals, created by smelting Stainless steel- Fe, Cr, Ni Stainless steel- Fe, Cr, Ni

22 Classifying Rocks Rocks are classified by how they formed, what they’re made of, grains (texture) Rocks are classified by how they formed, what they’re made of, grains (texture) Rocks are made up of minerals- aggregate Rocks are made up of minerals- aggregate There are 3 general classes of rocks- Igneous, Sedimentary, Metamorphic There are 3 general classes of rocks- Igneous, Sedimentary, Metamorphic

23 Igneous Rocks…are formed when lava and magma crystallize to form solid rock- Igneous Rocks…are formed when lava and magma crystallize to form solid rock- Extrusive/ Volcanic- formed on surface, shiny and glassy Extrusive/ Volcanic- formed on surface, shiny and glassy Intrusive/ Plutonic- formed beneath surface porphyritic- cools in 2 stages and forms in different sized crystals Intrusive/ Plutonic- formed beneath surface porphyritic- cools in 2 stages and forms in different sized crystals

24 Igneous Rocks Plutonic- gabbro, granite, monzonite, granodiorite Volcanic- basalt, pumice, obsidian, rhyolite (what the Valle is made of)

25 Metamorphic Rocks…are formed when an existing rock is partially melted, squeezed, or both- changes on a mineral, chemical or structural level Metamorphic Rocks…are formed when an existing rock is partially melted, squeezed, or both- changes on a mineral, chemical or structural level Foliation- forms in layers/bands Foliation- forms in layers/bands Gneiss- metamorphosed GRANITE Marble- metamorphosed LIMESTONE Quartzite- metamorphosed SANDSTONE

26 Metamorphic Rocks Gneiss Schist

27 Sedimentary Rocks…are formed when sediments (sand, clay, and silt) are compressed and become solid rock Sedimentary Rocks…are formed when sediments (sand, clay, and silt) are compressed and become solid rock Erosion- surface broken and worn away (rain) Erosion- surface broken and worn away (rain) Deposition- sediment settles by water or wind Deposition- sediment settles by water or wind Compaction- process which pressure squeezes layers together Compaction- process which pressure squeezes layers together Cementation-during compaction, minerals dissolve in water and glue the layers together Cementation-during compaction, minerals dissolve in water and glue the layers together

28 Clastic, Organic, Chemical Clastic- rock fragments are squeezed together (shale, sandstone, conglomerate) Clastic- rock fragments are squeezed together (shale, sandstone, conglomerate) Organic- remains of plants and animals deposited into layers (coal, limestone- coral reefs) Organic- remains of plants and animals deposited into layers (coal, limestone- coral reefs) Chemical- chemicals precipitate out of water and form a rock layer by layer (limestone, travertine) Chemical- chemicals precipitate out of water and form a rock layer by layer (limestone, travertine)

29 Sedimentary Rocks Shale Conglomerate Sandstone

30 Plate Tectonics Plate Movements and convection currents drive the Rock Cycle by pushing rocks back into the mantle, where they melt and become magma again. Plate Movements and convection currents drive the Rock Cycle by pushing rocks back into the mantle, where they melt and become magma again.


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