## Making Numbers Real (Grades 4-6)

Here are a few interesting facts and figures about the current eruption (provided by the U.S. Geological Survey's Hawaiian Volcano Observatory). Total area covered by lava from January 1983 to December 1992 is 32 square mile (83 square km). The total volume of magma erupted is 925 million m3. The Puu Oo cone is 768 feet (234 m) tall. As of early 1993, Puu Oo Crater is about 650 by 980 feet (200 by 300 m) and about 200 feet (60 m) deep. The thickness of lava over Kalapana Gardens is 735 feet (23 m). Total losses due to the eruption exceed \$61 million.

These numbers will not mean much to most students. It is difficult to picture a square mile or a million of anything. The purpose of this activity is to make large numbers more realistic by placing them in a familiar context. Here are a few examples.

The area of Hilo is about 8 square mile (from Hilo Bay to Panaewa, from Highway 11 to Komohana Street). The current eruption has covered four-times this area. The area of Kilauea Caldera is about 5 square mile. The current eruption has covered about six times this area. If those comparisons are too abstract, the area of a football field, about 6,000 m2 may be more familiar. Roughly 14,000 football fields would fit in the area covered by the current eruption.

The volume of the Kilauea Caldera is about 1 km3 (2.5x4x0.1 km). The volume of magma erupted is 925 million cubic m or about 0.9 cubic km. In other words, the volume of magma erupted since 1983 is roughly the same volume as the caldera. Note that volume of magma is not the same as the volume of lava flows because the gas dissolved in the magma expands as it erupts. If we wanted to store the magma in a vessel with an area of a football field, it would have to be 154,000 m high!

The height of the Puu Oo cone, the tallest volcanic feature on Kilauea Volcano, is 768 feet. The Bay Shore Towers apartment building on Hilo bay front is about 200 feet tall. Four of these buildings stacked on top of each other provides an estimate of the height of the Puu Oo cone.

Puu Oo Crater is about 650 by 980 feet (200 by 300 m) and about 200 feet (60 m) deep. In more familiar terms, the crater floor is about the size of 10 football fields. The crater is as deep as the Bay Shore Towers apartment building is high.

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