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<br />Age <br /> <br />An exam1nat1on of the Slumgul110n earthflow by two Un1ted States <br />Geolog1cal Survey geolog1sts 1n 1958 (Crandell, D. R. and Varnes, D. J.) <br />shows that the lower part of the earthflow 1s stable but that a younger <br />flow 1s slowly mov1ng down-slope over the older one. Rad1ocarbon age <br />dat1ng from wood 1ncorporated 1n the older flow 1nd1cates that the older <br />flow 1s 700! 200 years old. The oldest 11v1ng trees on the older flow <br />.are about 700 years old (1nd1cated by the number of tree r1ngs counted 1n <br />the trees). The oldest tree found near the toe of the act1ve younger flow <br />1s a dead spruce w1th 330 growth r1ngs suggest1ng that the younger flow 1s <br /> <br />probably not more than about 350 years old. <br /> <br />THE ACTIVE EARTHFLOW <br /> <br />The act1ve flow 1s about 2.4 m11es long, 500 to 1,000 feet w1de, and <br /> <br /> <br />or1g1nates at the same source as the older flow (Plate II). It descends <br /> <br /> <br />from 11,400 feet to 9,700 feet at an average grad1ent of 700 feet per m11e. <br /> <br /> <br />The toe of th1s younger, act1ve flow, 1s steep and unstable. It can eas11y <br /> <br />5 <br /> <br />C) <br />C) <br />C) <br />en <br />CD <br />CA <br />