Geo 101 Lab 1 Measurements and Measuring-4

Cochise Community College Geology 101 Instructor: J.Deakin Laboratory One Observing and measuring Earth Materials and Processes Objectives: 1. Know what the geologic record is and how it is similar yet different from a book. 2. Know that Geology is based on a logical, testable process of science that is ground truthed with data obtained by direct observation, investigation and measurement in the field and in the laboratory. 3. Measure and calculate length, area, volume, mass and density of Earth materials using basic scientific equipment and techniques. 4. Develop and test physical and quantitative models of isostasy based on floating wood blocks and icebergs. Apply these concepts to basalt and granite densities to calculate the isostasy of average blocks of oceanic and continental crust. Introduction: Thinking About Time Two key features of geoscientists' temporal thinking distinguish them from the general population: They take a long view of time, and they expect low-frequency, high-impact events. Geoscientists have internalized the vastness of the age of the Earth and the relative brevity of human history. They can envision Earth in states drastically different from the planet they have personally experienced: an Earth without humans, an Earth without life, a hothouse Earth, a snowball Earth. In the long view of time, exceedingly slow processes such as erosion or evolution can effect huge changes, such as the removal of a mountain or the establishment of new species. Infrequent but powerful processes, such as floods, volcanic eruptions, landslides, and asteroid impacts, are routine rather than abnormal when considered across the whole of Earth's history. Most People Do Not Understand Geologic Time Substantial impediments stand in the way of society achieving a broad understanding of geologic time. Geologic time involves scales and events far removed from human experience; thus, envisioning the cumulative impact of slow processes or infrequent events over geological timescales is not intuitive. Scientists' timekeeping tools rely on exponential numbers, ratios, and proportional reasoning, all of which present well- documented difficulties for many students. Finally, some religious teachings oppose the idea of an old Earth. The most widely known geologic feature in the United States is probably the Grand Canyon. It is a mile deep and cuts through millions of rock layers that are like pages of an immense stone book of geologic history called the geologic record. The layers are like pages and vary in thickness, but no one layer is exactly like another. Each has distinguishing features such as tiny microscopic fossils or grains of sand and some have large fossil trees, dinosaur bones or ancient stream channels. These stone pages have recorded the events of the past and are there for us to read. 1

From:httphttp://images.nationalgeographic.com/wpf/media-live/photos/000/696/cache/skywalk-grand-canyon- arizona_69640_990x742.jpgl Spatial and Temporal Scales Spatial scales are used by geologists to study Earth materials from the smallest atoms to the entire globe. At each spatial scale of observation, they identify materials and characterize relationships. Each scale is related to the others as shown in the table below. SCALE OF OBSERVATION USED TO STUDY THINGS LIKE…. MEASURED IN…. GLOBAL ENTIRE PLANET AND ITS INTERACTIVE SPHERES THOUSANDS OF KILOMETERS OR MILES REGIONAL PORTIONS OF OCEANS, CONTINENTS, COUNTRIES, PROVINCES, STATES OR ISLANDS KILOMETERS AND MILES 2

From: http://factsanddetails.com/world.php?itemid=2213&catid=51&subcatid=323 Questions: 1. Match each item below with the appropriated scale that should be used to study it. a. The Grand Canyon ______________ b. The Mississippi River______________ c. The Earth’s Atmosphere______________ d. The Paul Spur Reef (this is located on highway 80 towards Bisbee, see picture at end of lab) _______________ e. The arrangement of atoms in a diamond________________ 4

f. A quartz crystal_____________ 2. Recall that the geologic record is the millions of rock layers that record events and times in geologic history. Also recall that the geologic time scale is a chart showing named intervals of the geologic record and their ages in millions of years. a. Compare and contrast the geologic record with a history book. How are they the same? How are they different? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ _______________In what geologic period of time did the first amphibian appear on Earth? _________________________________ b. What era was this? ________________________________ c. How many years ago was this? ________________________ d. How old is the Earth in millions of years? e. How long ago did man evolve? _________________________ f. When did the dinosaurs go extinct? ____________________ 3. During the Paleozoic, 290 to 350 million years ago two periods called the Mississippian and Pennsylvanian occurred. These two periods are lumped together and often referred to as the Carboniferous. Why do you think geologists call this time the Carboniferous? ______________________________________________________________________________ ______________________________________________ Field Geology and Lab Work The most reliable information about Earth is obtained by direct observation, investigation and measurement in the field and laboratory. Most geologists study outcrops – field sites where rocks crop out, stick out of the ground. The outcrops are comprised of minerals. Samples obtained in the field are often moved to the lab for further analysis. Physical and chemical analysis and tests can be done to determine the composition of the rock sample. Many times the rocks are crushed and powdered then put into a solution where a qualitative analysis is performed to determine the chemical composition. This technique is often used at mines to determine the percentage of gold, silver or other precious metals in an ore (host rock) and is called an assay. In an assay both a qualitative and a quantitative assessment are performed to determine how much and what type of elements are in the sample. The mineral chalcopyrite is a good example. Chalcopyrite is a copper bearing mineral that is mined, crushed, put into solution with detergents and water, and finally agitated. The chalcopyrite rises to the surface because it is less dense then the other constituents. These small grains are skimmed off and then smelted (roasted) to separate the copper from the other parts of the chalcopyrite and melted rock (slag). The remaining copper powder is then leached in sulfuric acid and subjected to electrolysis, whereupon the copper is 5

5. How could you determine the density of water in g/cm 3 . Devise a procedure and then use it to actually do it? Show your data and calculations. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ____________________________________________________________________________ 6. Obtain a small lump of clay and determine its density in g/cm 3 . Explain your procedure and show your calculations for the density calculation. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ____________________________________________________________________________ 7. Modeling clay sinks in water. a. Why? __________________________________________ b. What could you do to the clay to make it float on water? Try your hypothesis and experiment until you get the clay to float? _____________________________________________ c. When you get the clay to float, why does it float? ______________________________________________ 8. The density of the following Spheres are listed a. Atmosphere = 1.2k g/m 3 b. Cryosphere = 920k g/m 3 c. Hydrosphere =1000k g/m 3 d. Lithosphere = 2800k g/m 3 How is the distribution of the Earth’s spheres related to their relative densities? In other words, how are the located relative to each other? ______________________________________________________________________________ ______________________________________________ Density, Gravity and Isostasy Archimedes, a Greek scientist, experimented with floating objects. One of the things he noticed was that when an object was submersed in a liquid the object displaced some of the water. Some objects floated with a portion of their bottoms below the surface level of the liquid. In any case, the surface level of the water rises when you put an object into it. Archimedes realized that every floating object is also pushed upward by a buoyant force that is equal to the weight of the displaced fluid. This is now called Archimedes Principle. Buoyant force is caused as gravity pulls on the mass of a fluid causing it to exert a fluid pressure on submerged objects that increases steadily with increasing depth into the fluid. The bottom of an object will have more force against it because it is lower in the fluid, the top of the object will have less force on it. It is these differences in force that give rise to the buoyant force. You have experienced the buoyant force if you have ever tried to pick up another person in the water. The task is easy because the water exerts an upward force on the person making them seem to “weigh” less. In the late 1800’s geologists began to realize that sea level has not always been constant. Sea level is in fact changing all the time. If the volume of ocean water changes in response to climate or other factors, then sea level can change. It is a known fact that melting of ice caps and glaciers adds more water to the world’s oceans and this causes changes in sea level. But as the ice caps melt there is less weight on the continents, this causes the land level to change . We know that the crust of the Earth floats on the mantle. It stands to reason that if we reduce the weight on the land the crust will be “buoyed” up out of the mantle. This is indeed happening in many parts of the world. The country of England is experiencing an isostatic rebound on its northern side. In other words, it is rising higher above the ocean on its northern edge since the end of the last ice age because all of the ice that “weighed” it down is now gone. Portions of Canada are also experiencing the same thing. Continents can also rebound when mountain ranges are eroded. Less mountain means 7

less weight so the continent pops back out of the mantle. This means that the continents are buoyed up by the more fluid mantle of the Earth. The mantle is mostly composed of a rock type called Peridotite which has a high density. The different blocks of the crust reach a point where they are in isostatic equilibrium. This whole concept is referred to as Isostasy. From: http://static.newworldencyclopedia.org/f/fd/Glacier_weight_effects_LMB.png From: http://www.eoearth.org/files/120601_120700/120672/Mountain_building_diagram.gif 9. Obtain a block of wood from your kit and determine its density in g/cm 3 . Show your calculations. __________________________________________________________________ 10. Float the same block in a bowl of water and attempt to mark the equilibrium line (waterline). Estimate the percent of the block that is below the water line? ___________________________________________________________________ 8 Here we see that as the mountain erodes, the entire crust that remains is buoyed back up out of the mantle.

Square inches (in2) x 6.5 = square centimeters Square feet (ft2) x .1 = square meters Square yards (yd2) x .8 = square meters Acres x .4 = hectares Cubic feet (ft3) x .03 = cubic meters Cords (cd) x 3.6 = cubic meters Quarts (lq) (qt) x .9 = liters Gallons (gal) x .004 = liters Ounces (avdp) (oz) x 28.4 = grams Pounds (avdp) (lb) x .5 = kilograms Horsepower (hp) x .7 = kilowatts Metric to English Metric English Centimeters (cm) x .39 = inches Meters (m) x 3.3 = feet Meters (m) x 1.1 = yards Kilometers (km) x .6 = miles Sq. centimeters (cm2) x .2 = square inches Square meters (m2) x 10.8 = square feet Square meters (m2) x 1.2 = square yards Hectares (ha) x 2.5 = acres Cubic meters (m3) x 35.3 = cubic feet Liters (l) x 1.1 = quarts (lq) Cubic meters (m3) x 284.2 = gallons Grams (g) x .04 = ounces (avdp) Kilograms (k g) x 2.2 = pounds (avdp) 10

Paul Spur Reef Highway 80 near Douglas, AZ Answer Sheet for Lab 1 Name:____________________ 11

b. ________________________________________________________ c. ________________________________________________________ 8. _____________________________________________________________ _____________________________________________________________ 9. (show work) 10._____________________________________________________________ _____________________________________________________________ 11._____________________________________________________________ _____________________________________________________________ 12._____________________________________________________________ _____________________________________________________________ 13._____________________________________________________________ _____________________________________________________________ 13