https://bereket-haileab.geology.sites.carleton.edu/files/original/ef732a9f5f232712ad19da43fe743b03.jpg 7dc04dedb510e7628c954de0058f9576 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section and hand sample Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-175d Subject The topic of the resource Basalt Description An account of the resource Major Minerals: clinopyroxene, orthopyroxene, plagioclase, brown glass, iddingsite Minor Mineral: aragonite, oxide Mineralogy Comments: Aragonite occurs within vesicular cavities. Sample BH250-175d was collected from Grand Canyon during field trips that I lead for Carleton Alumni trip. The sample exhibits a typical basaltic texture and well-developed hexagonal columnar jointing. Vesicles within the flow are commonly filled with secondary minerals, including aragonite. Aragonite (CaCO₃) is a carbonate mineral chemically identical to calcite but differing in crystal structure. As a polymorph of calcite, it crystallizes in the orthorhombic system and is optically biaxial negative, with a small 2V angle of ~18°. Its high birefringence produces multiple isochromes around the melatope in conoscopic interference figures. Although aragonite’s birefringence is similar to calcite, the two can be distinguished in thin section by their distinct optical properties. Photomicrographs of the sample display both the basaltic textures and the vesicle-filling aragonite, including its characteristic optical features. For comparison, see the thin sections and photomicrographs from sample BH250-39, which also contain aragonite. Basaltic lava flows are widely exposed throughout the Grand Canyon. Some of these flows entered the canyon, temporarily damming the Colorado River while advancing downstream along the river channel. The river eventually breached these natural dams and carved new channels, leaving behind remnants of the lava flows that can be traced up to 120 km downstream. These remnants of the lava flows are now preserved as inverted topography (see photographs of the outcrops). These lava flows originated from the Uinkaret volcanic field on the North Rim of the Grand Canyon creating natural dams that are estimated to have been over 600 meters (2,000 feet) high. Another striking example of inverted topography, shared by Frank H. Brown, is located in Kenya at 2°17'42.94"S, 38°11'33.09"E. There, a lava flow erupted from the Kenyan highlands, exploiting an existing river(s) course that flowed toward the Indian Ocean. The lava traveled nearly 800 km along this channel. I plan to collect a sample from this flow in the future to analyze its chemistry and determine the lava type responsible for such an extensive journey. Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Location: Pumpkin Spring Pool, Grand Canyon, Arizona, USA Nearby Feature: Grand Canyon GPS Coordinates: 35°54'58.39"N, 113°20'2.21"W Date A point or period of time associated with an event in the lifecycle of the resource August 2021 Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-175d. Housed at Carleton College in Minnesota. 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making the resource Bereket Haileab Contributor An entity responsible for making contributions to the resource Bereket Haileab 2V angle 2V(x) of 18 degrees Aragonite basalt Biaxial negative BXa(x) Calcite Polymorph Calcite vs Aragonite Carbonate Minerals Cavity Fill Minerals Colorado River Geology Grand Canyon Geology Grand Canyon Volcanism high birefringence Iddingsite igneous Inverted Topography Isochrome Lava flow from Kenya Longest Kenyan Lava Flow Longest Lava Flow mafic Pumpkin Spring Pool Uinkaret Volcanic Field volcanic