<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>K. L. Tanaka</dc:contributor>
  <dc:creator>D. H. Scott</dc:creator>
  <dc:date>1986</dc:date>
  <dc:description>&lt;p&gt;&lt;span class="TextRun SCXW26880284 BCX8" lang="EN-US" xml:lang="EN-US" data-contrast="auto"&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;The &lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;r&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;egional topographic swell centered in the &lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;Tharsis&lt;/span&gt; &lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;Montes&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt; and Syria Planum extends over one-third&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt; of the map area (U.S. Geological Survey, 1976). Within this high region are the four largest and &lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;youngest volcanoes on Mars: Olympus Mons, &lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;Arsia&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt; Mons, Pavonis Mons, and &lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;Ascrae&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;us&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt; Mons. The latter three collectively form the large northeast-trending, volcanic mountain&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt; chain of the &lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;Tharsis&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt; Montes. This volcanic chain lies athwart the global &lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;highland&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;-&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;lowland boundary that transects the western equatorial region. The boundary, where not covered b young lava flow&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;s, is marked by a gentle, irregular scarp bordered by clusters of low&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt; knobby hills. It separates the relatively smooth, flat, spar&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;sely cratered northern plains from the higher, rougher, more densely cratered plateau terrain of the &lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;southern highlands&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;. A vast system of canyons, the Valles &lt;/span&gt;&lt;span class="SpellingError SCXW26880284 BCX8"&gt;Marineris&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;, originates in Noctis&lt;/span&gt; &lt;span class="SpellingError SCXW26880284 BCX8"&gt;Labyrinthus&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;, just east of the &lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;Tharsis&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;-Sy&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;ria swell, and extends eastward for several thousand kilo&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;meters. Ancient rivers channels appear to have sources in canyons and chaotic terrain north of Valles &lt;/span&gt;&lt;span class="SpellingError SCXW26880284 BCX8"&gt;Ma&lt;/span&gt;&lt;span class="SpellingError SCXW26880284 BCX8"&gt;rineris&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt; and in a large fissure at the head of the Mangala &lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;V&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;alles. Visible remnants of large circular&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt; basins are not as common on Mars as on the Moon, probably because of more active &lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;erosion and deeper burial on Mars by eolian and fluvial activity&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt; and by widespread volcanism on both the highlands and plains. The youngest and &lt;/span&gt;&lt;span class="ContextualSpellingAndGrammarError SCXW26880284 BCX8"&gt;b&lt;/span&gt;&lt;span class="ContextualSpellingAndGrammarError SCXW26880284 BCX8"&gt;est preserved&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt; impact basin on Mars, lying in the western hemisphere&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;, is more than 1,00&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;0&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt; km across. It has a broad flat &lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;floor &lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;(&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;Argyre&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt; Planitia) covered by eolian materials and volcanic flows&lt;/span&gt;&lt;span class="NormalTextRun SCXW26880284 BCX8"&gt;; the floor is several kilometers below its encompassing rough mountainous rim.&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.3133/i1802A</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>U.S. Geological Survey</dc:publisher>
  <dc:title>Geologic map of the western equatorial region of Mars</dc:title>
  <dc:type>reports</dc:type>
</oai_dc:dc>