Image courtesy of D. Roddy through the Lunar and Planetary Institute. Code of Conduct The moons surface is riddled with craters ranging in size and structural complexity, and billions of years ago before life emerged, the Earth looked the same way. Space shuttle image STS51I-33-56AA, courtesy of the Lunar and Planetary Institute. 17 0 obj Indeed, impact craters are one of the most common geological landforms on the majority of rocky terrestrial planets, asteroids, and many of the rocky and icy moons of the inner and outer Solar System. Like the other planets, Earth formed . The Vredefort impact crater, about 100 kilometers (60 miles) from Johannesburg, South Africa, was formed just a little over 2 billion years ago. <>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 17 0 R/Group<>/Tabs/S/StructParents 1>> The shock wave fractures the rock and excavates a large cavity (much larger than the impactor). They are typically filled with impact rocks (impactites) in the form of impact melt rocks,suevitesand different kinds ofbreccias. Describe the breakage as either irregular or conchoidal (has the appearance of broken glass)HardnessResistance to scratching or abrasion.Use minerals of known hardness from the Mohs Hardness Kits. Simple Craters . The ejecta of the larger crater is different from that of the smaller crater. 1 0 obj The legend is shown at the bottom with different units or features present within the crater. Smaller planets have less gravitational "pull" than large planets; impactors will strike at lower speeds. How scientists solved the riddle of these mysterious landforms. What influences the size and shape of a crater? The texture of an igneous rock does not refer to the roughness or smoothness of the surface. Scientists rely on geophysical images for information about its size and shape. Craters come in two flavors: those that aren't caused by asteroids or comets, impact craters, are formed by powerful volcanic explosions. Impact craters are relatively shallow, so these "dents" in Earth's rocky . xZms|fl d;NrHIM. 13). The three stages of impact crater formation. 12. This can be easily confused with a crystal face and is the most difficult properties for students to master.ColorVisible light spectrum radiation reflected from a mineral.Look at the sample and determine its color - white, black, green, clear, etc.Crystal FormGeometric shape of a crystal or mineral.Examine and describe the geometric shape of the mineral - cubic, hexagonal, etc. The meter scale indicates water depth. In concurrence with this result, the crater age . The Earth used to look just like that.. Here again, the difference is obvious: In the case of cobble-into-mud or raindrop impacts the craters are not much larger than the projectile (Fig. 2) we may think it somehow formed from an identical mechanism. Terraces are a common feature of many large craters---for another example, look at the crater Theophilus. PAGE 3 PAGE 1 ! A peak ring crater (Clearwater West, Canada, 32 km diameter). The impact sprays material ejecta out in all directions. How looks an impact crater that was produced by an oblique impact? Larger impacts also still occur, but these are much more rare. These fragments or clasts can be very fine (ash) or coarse (lapilli) or very coarse (bombs and blocks). Terms of Use, Copyright document.write(new Date().getFullYear()); Biologic sedimentary rocks are which form as the result of the accumulation of organic material or biologic activity. You will have to calculate an approximate image scale from the height of the peak in the foreground.) Quartzite is composed of quartz sand grains. What would happen if a loosely bound impactor such s this were to strike Earth? 10. The general story of an impact follows a pretty predictable process. <> 22. Not a model for impact crater formation. Reuyl Crater Central Peak, as seen by HiRISE. Craters produced by the collision of a meteorite with the Earth (or another planet or moon) are called impact craters. Google Earth image. Mineral Physical Properties ChartPHYSICALPROPERTYDefinition*Testing MethodCleavageBreakage of a mineral along planes of weakness in the crystral structure.Examine the mineral for areas where the mineral is broken. Examine the caldera (labeled A) and describe its shape. One of the most well-known craters on Earth is Meteor Crater, which is near Winslow, Arizona. Sedimentary rocks are rocks composed of sediment. The high-speed impact of a large meteorite compresses, or forces downward, a . endobj Scratch the unknown mineral with a known hardness to determine which mineral is harder. A bowl-shaped simple crater (Wolfe Creek, Australia, 900 m diameter). endobj On Mars, meteor storms 100 million years ago may have literally shaken the Red Planet to the core and destroyed its magnetic field. Sedimentary rock identification is primarily based on composition. Sometimes the force of the impact is great enough to melt some of the local rock. | What process do you think formed Apollinaris Patera? Which is larger, and by how much? Learn how these processes work and how they formed more than 300.000 craters on the Moon. Lava later flowed across the low floors of the basins, giving them a darker, smoother appearance than the surrounding, brighter highlands. The bottom line is, everything that happened on the moon happened on the Earth, said David Kring, crater expert and team leader for Center for Lunar Science and Exploration. The more mass it has the bigger the impact. Copernicus is a large crater (93 kilometers or 60 miles wide) on the Moon. These are impact craters, each of which was formed when an asteroid or comet collided with the Moon's surface. The impactor is shattered into small pieces and may melt or vaporize. The same chemical composition, but two different crystalline structures - therefore, two different minerals. During the final modification phase, the remainder of ejecta partially refills and rings the crater site, and debris forms a rich mineral composite called breccia. Dunite has an ultramafic composition yet is apple green to yellowish green in color. Lastly, pyroclastic texture is composed of volcanic fragments. 14. The cratering process will help reveal what type of material makes up the nucleus (or at least the outer layer), and therefore how the comet formed and evolved. Look for areas where the light reflects from planar surfaces. 8. Gosses Bluff (Tnorala) Pingualuit Crater. i~4?7Z"UJmiCwbes%7Vo}bf_iK4Ev, u4J_8(Vjj#W]^`:*I23SPPEX `p-1sU?"_F4I=?^i(.i]V Fortunately determination of the exact chemical composition is not necessary. Martian shield volcano, Olympus Mons. (a) Geomorphic map of Reuyl crater. 7. h_X CJ h_X 5B* CJ ph h \ I noticed the young crater has an odd shape, non-circular, almost diamond-shaped. In an introductory level lab it is impossible for us to determine these two aspects of a mineral. These stages are: the contact and compression stage (Fig. The dark brown to black color is the most obvious characteristic. ), 1987, Glossary of Geology. largest craters on Europa, Ganymede, and Callisto formed in an icy crust (Io's crust is dominated by silicates, see Chap ter 14). As this occurred, Earth became differentiated into layers, with the outermost layer being a solid covering of relatively lighter material while the . The crater is 2 kilometers (about 1 mile) wide. The excavation stage of impact cratering. When first we see images of the famous one-kilometer (0.75-mile) bowl-shaped Barringer meteorite crater in Arizona (Fig. How can you tell? Both are black in color, and is composed of carbon. Craters of the Moon is a large lava flow field with cinder cones, spatter cones, lava tubes, volcanic bombs and tree molds. endobj Justify your answer. Location: 24S, 245W. 1}bRX12AMAWQe'=u"tP]]!|SdX"uk3&~m?B?_OuG+ s6S x> PY4/'!~OFZUT=ayZBxY`=j 0 "(_Cye@2UGDkA;$V+ "+.m e. Igneous rocks can be identified by the determination of the composition and texture of the rock. If windstreaks are dust deposits formed downwind from the craters, what wind direction is indicated here? Note: This is a large Adobe Acrobat PDF file: "craters_activity.pdf" (8.5 Mb), so you may want to download to your computer. (80 km diameter). Explain how you can tell. Craters are roughly circular, excavated holes made by impact events. This flow field grows with time, and the rock mass flow is directed upwards, sideward and downwards. <> %PDF-1.5 (Viking MDIM Volume 4) 15. For instance, the famous Chicxulub crater in Yucatan, Mexico, is thought to be the site of the meteor impact that instigated the K-T event, which wiped out the dinosaurs in a mass extinction that affected much of life on Earth. The contact and compression stage of impact cratering. Valley systems cut through many of the cratered terrains of Mars and have characteristics analogous to water-cut valleys on Earth. Felsic compositions are rich in silica (SiO2). Early in the formation of our solar system (before 3.9 billion years ago) there was lots of large debris striking the surfaces of the young planets and moons; these older impact basins are larger than the more recent craters. 16. Most obsidian is felsic in composition, yet typically it will have a very dark color (dark brown to black). It is true meteorites crashing as stones from the sky at free-fall velocity may in fact produce small craters in the ground similar to mud and hailstone craters. 4. The composition of clastic sedimentary rocks is divided into three types - clay/silt, sand and gravel. <> The transition from simple to complex craters occurs at about 1.5 to 4 km (depending on the target rocks) final diameter for terrestrial craters and is much larger (c. 15 km) for craters on the Moon. Were still searching for a clue to deduce that.. 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