Multi-Hazard Mitigation Plan: 08. Lava And Vog

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Chapter 8:Hazard Analysis—Lava and VOG 8.1.2.3 Effects on Plants Sulfur dioxide must enter leaf mesophyll tissue, through stomata (natural openings in leaf surfaces that regulate gas exchange), to cause plant injury. Once S02 enters the moist mesophyll tissue, it combines with water and is converted to sulfuric acid which burns plant tissue. The general effects of S02 exposure to plants may vary and depend upon plant species, age, and the S02 dosage; these effects may include: • reduced seed germination • enhanced susceptibility to other diseases • foliar necrosis (spots,blight) • epicuticular wax erosion • rupture of epidermis,plasmolysis • reduced chlorophyll content • increased membrane permeability of plant leaves • decreased plant growth(root length, shoot length,leaf numbers) • plant organ or entire plant death 8.1.3 Ashfall Large amounts of ash were deposited both up- and down-wind from the large explosive events of 1790 and 1924. By contrast, the 2008-ongoing Kilauea summit eruption has been persistently producing small amounts of ash punctuated by brief periods of increased production. HVO ash leachate analyses of samples collected near Halema'uma'u after explosive events in March and April found high levels of fluoride and some metals (cadmium, copper, lead, and chromium for example). These levels were elevated but not high enough to warrant immediate concern because of the low ash emission rate measured, even during explosive events. Substances like fluoride could be of concern downwind of any eruption if substantial accumulation occurs, either by increased ash deposition or by a significantly prolonged eruption. 8.2 Significant Historic Events The recorded history of volcanic activity in Hawaii begins with the arrival of the Christian missionaries in the early 1800's and those that are known from oral traditions of the Hawai- ians. Additional information on prehistoric eruptions is based on geologic mapping and dat- ing of old lava flows. 8.2.1 Mauna Loa Mauna Loa has had 33 historically recorded eruptions, most of which have occurred at the summit. Approximately 25% of the eruptions have started on the east-northeast rift zone and another 25% began in the southwest rift zone.37 During the period from 1832 to 1950, 37 Draft Lava Flow Hazard Mitigation Plan,2002 8-9 Hawaii County Multi-Hazard Mitigation Plan