Researchers estimated that the volcanoes formed during a period 81 million to 45 million years ago. Tarduno and his team determined where the volcanoes formed by analyzing the rock for the magnetic mineral magnetite. While hot lava from a volcanic eruption cools, tiny grains within the magnetite align with the Earth's magnetic field, and lock in place once the rock solidifies. Researchers were able to verify the latitudes at which the volcanoes formed by measuring the grains' orientation within the magnetite. Paleomagnetists concluded that the Hawaiian hotspot had drifted southward sometime in its history, and that, 47 million years ago, the hotspot's southward motion greatly slowed, perhaps even stopping entirely. The possibility that the Hawaiian islands became older as one moved to the northwest was suspected by ancient Hawaiians long before Europeans arrived. During their voyages, seafaring Hawaiians noticed differences in erosion, soil formation, and vegetation, allowing them to deduce that the islands to the northwest (Niihau and Kauai) were older than those to the southeast (Maui and Hawaii). The idea was handed down the generations through the legend of Pele, the Hawaiian goddess of volcanoes. Pele was born to the female spirit Haumea, or Hina, who, like all Hawaiian gods and goddesses, descended from the supreme beings, Papa, or Earth Mother, and Wakea, or Sky Father. According to the myth, Pele originally lived on Kauai, when her older sister Nāmaka, the Goddess of the Sea, attacked her for seducing her husband. Pele fled southeast to the island of Oahu. When forced by Nāmaka to flee again, Pele moved southeast to Maui and finally to Hawaii, where she still lives in Halemaʻumaʻu at the summit of Kīlauea. There she was safe, because the slopes of the volcano are so high that even Nāmaka's mighty waves could not reach her. Pele's mythical flight, which alludes to an eternal struggle between volcanic islands and ocean waves, is consistent with geologic evidence about the ages of the islands decreasing to the southeast. Three of the earliest recorded observers of the volcanoes were the Scottish scientists Archibald Menzies in 1794, James Macrae in 1825, and David Douglas in 1834. Just reaching the summits proved daunting: Menzies took three attempts to ascend Mauna Loa, and Douglas died on the slopes of Mauna Kea.