jancancook
Posts : 1136 Join date : 2011-01-02
| Subject: The volcano is so old that it experienced Fri Nov 11, 2011 3:29 pm | |
| The volcano is so old that it experienced, and recorded, a reversal of magnetic polarity (a change in the orientation of Earth's magnetic field so that the positions of the North and South poles interchange) that happened 780,000 years ago. Fifty different flow units in the top 140 m (459 ft) of exposed strata in the Pololu section are of normal polarity, indicating that they were deposited within the last 0.78 million years. Radiometric dating ranged mostly from 450,000 to 320,000 years ago, although several pieces strayed lower; this indicated a period of eruptive history at the time.[2] Cliffs as seen from the beach at Waipiʻo Valley Kohala was devastated by a massive landslide between 250,000 and 300,000 years before present. Debris from the slide was found on the ocean floor up to 130 km (81 mi) away from the volcano. Twenty kilometers wide at the shoreline, the landslide cut back to the summit of the volcano, and is partially, if not largely, responsible for the volcano losing 1,000 m (3,281 ft) in height since then. The famous sea cliffs of the windward Kohala shoreline stand as evidence of the massive geologic disaster, and mark the topmost part of the debris from this ancient landslide.[1] There are also several other unique features found on the volcano, all marks made by the decimating collapse.[2] online crmReal Estate Hervey Bay | |
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