Field, laboratory, and library manual in physical geography . Fig. 18. Mud Cracks in the Bed of an Intermittent Stream,Southern California side ? This hill is a volcanic neck. How has it been made ?(See picture and cross section on the page opposite the map inFolio 2.) How deep is the crater from the rim to the smalllevel area just west of the neck? What is the average elevation above sea level of the mesaSierra Chivato? of the region 10 or 15 miles northwest ofWillow Spring? (Count down from the contour line of 7000. Fig. 19. Columns of Basalt from an Old Lava Plow on the North Forkof the San
Field, laboratory, and library manual in physical geography . Fig. 18. Mud Cracks in the Bed of an Intermittent Stream,Southern California side ? This hill is a volcanic neck. How has it been made ?(See picture and cross section on the page opposite the map inFolio 2.) How deep is the crater from the rim to the smalllevel area just west of the neck? What is the average elevation above sea level of the mesaSierra Chivato? of the region 10 or 15 miles northwest ofWillow Spring? (Count down from the contour line of 7000. Fig. 19. Columns of Basalt from an Old Lava Plow on the North Forkof the San Joaquin River, California 125 126 PHYSICAL GEOGRAPHY MANUAL feet.) How much higher is the mesa than the surroundingregion ? Is the descent from the mesa abrupt or gentle ? With apointer trace the outline of the mesa. In which direction doesit extend farthest from Mt. Taylor? The author of Folio 2says, This is a volcanic mesa, formed by outflows of lavafrom the mountain and probably from other craters uponthe surface of the mesa. Across the Puerco river northeastof the Sierra Chivato is Cabazon peak, a volcanic neck morethan 1000 feet high. How many volcanic necks do you seebetween the Sierra Chivato and the Puerco river? Volcanicnecks were formed by the forcing of volcanic rocks, in amolten condition, up through overlying stratified beds. Thesebeds, which were much softer than the lava, have since beeneroded away, leaving the neck of lava standing by itself. EXERCISE XLVIIA CRATER Refer to the Crater lake (Or
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