How did the Hawaiian Islands form geologically? How could the relative age of the islands be determined? (In other words, how would you know which island was oldest, which was youngest, etc.)?
http://en.wikipedia.org/wiki/Hawaiian_Islands#Geology
The Hawaiian Islands were formed through a geological process involving volcanic activity. They are part of a chain of volcanic islands located in the Pacific Ocean, known as the Hawaiian-Emperor seamount chain.
The formation of the Hawaiian Islands began around 70 to 80 million years ago when a "hotspot" in the Earth's mantle created a volcanic eruption at a specific point on the Pacific tectonic plate. As the Pacific plate moved slowly over the hotspot, a chain of volcanoes formed. Each volcano was active for a period of time before becoming dormant as the hotspot moved.
The islands, from oldest to youngest, include Kauai, Oahu, Molokai, Lanai, Maui, and the Big Island of Hawaii. The Big Island is the youngest and most active, with ongoing volcanic eruptions, while Kauai is the oldest and has been eroding for millions of years.
Determining the relative age of the Hawaiian Islands is done through several geologic methods:
1. Radiometric dating: Volcanic rocks on the islands can be dated using radiometric techniques, such as potassium-argon dating or uranium-lead dating. These methods measure the decay of specific isotopes within the rocks to determine their age.
2. Stratigraphy: By studying the layers of volcanic rocks on each island, geologists can determine their relative order. Older layers are typically found below younger layers.
3. Erosion and weathering: Islands that are older have had more time to undergo erosion and weathering processes. Geologists can analyze the differences in topography, landforms, and soil development to infer the relative age of each island.
4. Fossil records: Fossils preserved within the volcanic rocks can provide additional clues about the relative age of the islands. By comparing the fossils found on different islands, scientists can determine their relative ages based on the known ages of the fossil species.
By combining these methods, geologists can construct a timeline of the Hawaiian Islands' formation and understand their relative ages. It is important to note that while the overall sequence of island formation is well-understood, the precise ages of individual islands may still be subject to ongoing research and refinement.