These high hazard estimates for Haleakala are based on the frequency of its eruptions. Haleakala has erupted three times in approximately the last 900 years. By way of comparison, both Mauna Loa and Kilauea have erupted more than a dozen times each in the last 90 years. Hualalai has an eruption rate comparable to Haleakala. All of Hualalai is rated as Hazard Zone 4. However, the frequency of eruption of a volcano is only one of the criteria on which hazards are based. The other important criterion is the lava flow coverage rate. Using the preliminary dates for Haleakala flows, only of lava flows have been emplaced in the last 900 years. In comparison, approximately of Hualalai are covered with flows 900 years old or younger and approximately on Kilauea and on Mauna Loa are covered by lavas less than 200 years old. Thus, Haleakala is a distant fourth in coverage rates.