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Grand Canyon Rocks “Those who write about the Canyon generally begin by saying that it is indescribable; then they undertake to describe it.” Joseph Wood.

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Presentation on theme: "Grand Canyon Rocks “Those who write about the Canyon generally begin by saying that it is indescribable; then they undertake to describe it.” Joseph Wood."— Presentation transcript:

1 Grand Canyon Rocks “Those who write about the Canyon generally begin by saying that it is indescribable; then they undertake to describe it.” Joseph Wood Krutch

2 Grand Canyon: Limestone The oldest known rocks on Earth come from the Mackenzie District of Canada’s Northwest Territories. They have been dated at 4 billion years old. It wasn’t until the later Precambrian era, around 1.8 bya to 500 mya, that the first carbonate sediments began to settle out of the oceans to eventually form limestone. The Bass Limestone, part of the GC Supergroup, was one of the first limestones.

3 Grand Canyon: Limestone The major component of all limestone is calcium carbonate, CaCO 3. This is the chemical name for the minerals calcite and aragonite. Calcite, aragonite, and dolomite, CaMg (CO 3 ), are estimated to make up 15 % of the earth’s sediments and sedimentary rocks, and about 2 % of the earth’s crust.

4 Grand Canyon: Limestone Carbonate minerals can be identified fairly easily because they all break down in acid. The carbon-oxygen bond in the CO 3 group becomes unstable in the presence of hydrogen ions (H + ) found in acids, and the carbon dioxide CO 2 forms. Calcite is the most common mineral noted for fizzing.

5 Grand Canyon: Limestone The reaction the occurs between hydrochloric acid and calcite is expressed: CaCO 3 + 2HCl CO 2 + H CaCl 2 calcium hydro carbon water calcium carbonate acid dioxide chloride

6 Grand Canyon: Limestone Calcification is the process by which certain organisms and algae extract calcium and carbonate ions from the surrounding seawater, oxidize the calcium, and deposit the resulting compound as solid material, either calcite or aragonite. Calcite is more common than aragonite and makes up the bulk of limestone and marble deposits on Earth.

7 Grand Canyon: Limestone Calcium ions are produced through the chemical weathering of rocks such as granite. As mountains of granite decompose, calcium ions are released and carried to the ocean by rivers and streams. Precipitation of calcium carbonate may occur by chemical or organic means. (Limestone created: Chem Weathering or Biological ways.) Many marine plants and animals extract calcium carbonate directly from seawater for incorporation into their shells.

8 Grand Canyon: Limestone Most limestones throughout the history of Earth formed in relatively shallow, warm seas. One ingredient all limestones have in common is calcium carbonate. Geologists identify a variety of different forms of limestone: Chalk is composed of almost pure calcite. A powdery, fine-grained rock, chalk may contain small amounts of silt or mud.

9 Grand Canyon: Limestone Reef limestones are mainly composed of the skeletons of marine organisms, such as corals. Today coral reefs grow in warm seas. The beautiful blue-green waters associated with these areas are indicators of lime-secreting blue-green algae. Sections of the Redwall Limestone in the GC include fossil corals and other reef-dwelling organisms, indicating a warm, tropical environment.

10 Grand Canyon: Limestone Reef limestones are mainly composed of the skeletons of marine organisms, such as corals. Today coral reefs grow in warm seas. The beautiful blue-green waters associated with these areas are indicators of lime-secreting blue- green algae. Sections of the Redwall Limestone in the GC include fossil corals and other reef-dwelling organisms, indicating a warm, tropical environment.

11 Grand Canyon: Limestone Coquina is a limestone formed almost entirely of sorted and cemented fossil debris, mostly small shells and shell fragments. The sorting of the fragments and type of organisms suggest that the material has been transported some distance and/or sorted by wave action. Freshwater limestones can be identified by the type of fossils it contains. It often includes snail shells.

12 Grand Canyon: Limestone Coquina is a limestone formed almost entirely of sorted and cemented fossil debris, mostly small shells and shell fragments. The sorting of the fragments and type of organisms suggest that the material has been transported some distance and/or sorted by wave action.

13 Grand Canyon: Limestone Freshwater limestones can be identified by the type of fossils it contains. It often includes snail shells.

14 Grand Canyon: Limestone Oöliths are small grains of sand, silt, or shells around which concentric layers of calcium carbonate are deposited. Oölithic limestones usually form in warm, shallow marine conditions where limy mud forms and in which agitation by waves, tides, and currents takes place.

15 Grand Canyon: Limestone Tufa is formed from cool freshwater sources rich in calcium carbonate. When the water is exposed to the atmosphere, carbon dioxide is released, precipitating calcium carbonate. In areas where limestone is common, tufa fills cavities in rocks and builds stalactites and stalagmites in caves. Travertine is harder and denser than tufa. It is often deposited around hot springs, such as Yellowstone National Park. It is found in the same places as tufa, including caves.

16 Grand Canyon: Limestone Tufa is formed from cool freshwater sources rich in calcium carbonate. When the water is exposed to the atmosphere, carbon dioxide is released, precipitating calcium carbonate. In areas where limestone is common, tufa fills cavities in rocks and builds stalactites and stalagmites in caves.

17 Grand Canyon: Limestone Travertine is harder and denser than tufa. It is often deposited around hot springs, such as Yellowstone National Park. It is found in the same places as tufa, including caves.

18 Grand Canyon: Limestone Stratigraphy is the study of the distribution and sequence of sedimentary rock layers. If two rock layers or strata contain the same group of fossils, they must be the same age. Lithostratigraphy is a subcategory of Stratigraphy in which geologists describe rock layers and their distribution.

19 Grand Canyon: Limestone Lithostratigraphy : organizes rock layers: Formations: layers with distinguishable characteristics and sequences of sediments. Members: smaller identifiable units that make up formations. Beds: the smallest distinguishable unit, often only a few centimeters in thickness, but different from the sediment above and below it.

20 Grand Canyon: Limestone Law (or principle) of Superposition states that in any undisturbed sequence of layered rocks, a particular bed must be older than any bed on top of it.

21 Grand Canyon: Limestone Law (or principle) of Superposition states that in any undisturbed sequence of layered rocks, a particular bed must be older than any bed on top of it. Law of Original Horizontality states that, when particles of sediment settle out of water or air, they form horizontal layers.

22 Grand Canyon: Limestone Law (or principle) of Superposition states that in any undisturbed sequence of layered rocks, a particular bed must be older than any bed on top of it. Law of Original Horizontality states that, when particles of sediment settle out of water or air, they form horizontal layers. An Unconformity is a gap in the geological record during which either no rocks were deposited or erosion of existing rocks took place.

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25 Grand Canyon: Rocks Sandstone Shale What is the third type of rock found in the Grand Canyon?

26 Making Limestone Sandstone Shale What is the third type of rock found in the Grand Canyon? What was the property of limestone that you observed during the “Acid Test?”

27 Making Limestone Sandstone Shale What is the third type of rock found in the Grand Canyon? What was the property of limestone that you observed during the “Acid Test?” In your journals, list what might be found in the seawater that would contribute to the fizz.

28 Making Limestone Double the recipe: Limestone Pg 39 binder. You may use a total of 2 spoons of plaster of paris. Do not change the amount of water added. Keep 30 ml. You may use a total of 8 spoons of the following materials Sand Oyster shells Powdered clay (You may add a shell fossil to the surface of your limestone layer.)

29 Making Limestone The chemical in the water that makes it similar to the ancient seawater is calcium hydroxide. Calcium hydroxide dissolved in water is called limewater (nothing to do with lime fruit). Ancient seawater contained many other dissolved chemicals as well, salts, acids, but the calcium hydroxide is the chemical of interest today.

30 Making Limestone What is a fossil?

31 Making Limestone What is a fossil? A fossil is any remains, trace, or imprint of a plant or animal that has been preserved in the earth’s crust since some past geological or prehistoric time. A looser definition is any evidence of past life.

32 Making Limestone Testing for Calcium Carbonate/ hydroxide w/ hydrochloric acid Journal: Make a table MaterialFizzNo Fizz Small cup “white stuff” Large cup: top layer “sedimentary” Rock # __ from North Canyon Rock # __ from Nankoweap Canyon

33 Biological Process Remains of marine animals. Their shells and skeletons are deposited on the bottom of the ocean The calcite and other minerals may harden into limestone. Remains of animals may also be buried in the carbonate muds and eventually turn into fossils.


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