 The Quizapu Crater is almost perfectly circular , and rises to a prominence of 150 to 250 meters ( 490 to 820 ft ) above the surrounding portions of the volcano . <unk> at 3 @,@ 292 meters ( 10 @,@ 801 ft ) in elevation , Quizapu is one of the highest known Plinian craters . The radius of the crater floor , which is the current inner vent , is around 150 meters ( 500 ft ) , while the radius of its rim is 300 – 350 meters ( 980 – 1 @,@ 150 ft ) . The crater floor lies at 2 @,@ 928 meters ( 9 @,@ 606 ft ) , and the rim lies 150 – 300 meters ( 500 – 1 @,@ 000 ft ) above that , giving the walls an average slope of 34 – 35 degrees ( close to the angle of repose ) . The western wall is cut by two long , dacitic lava flows : probably the remnants of a dome or an eruption . The crater is surrounded by debris from its 1932 eruption , and topped by layers — 50 meters ( 160 ft ) thick — of mafic scoria and ash . 
