Geological History
Manoa Falls is a popular waterfall located in Manoa Valley on the island of Oahu, Hawaii. The geological history of Manoa Falls is closely tied to the island's volcanic origins. Here's an overview of the geological history:
Formation of Oahu: Oahu, like the rest of the Hawaiian Islands, was formed through volcanic activity. The Hawaiian Islands are the result of a hot spot beneath the Pacific Plate, where a plume of magma rises from deep within the Earth's mantle to create new land. Oahu is the result of multiple volcanic eruptions over millions of years.
Formation of Manoa Valley: Manoa Valley itself was formed through a combination of volcanic and erosional processes. The initial volcanic activity created the topography of the island, and over time, the forces of erosion, primarily from rainwater, helped shape the valleys, including Manoa Valley.
Formation of Manoa Falls: Manoa Falls was formed by the continuous flow of water from the mountains and the underlying basalt rock. Rainwater that falls in the higher elevations of the Ko'olau Range, which includes Manoa Valley, feeds into the many streams and rivers that cut through the valleys on Oahu. Manoa Falls is one of the prominent waterfalls in this area, resulting from the convergence of these water sources.
Geological Composition: The geological composition of Manoa Falls is primarily basalt rock, which is typical of volcanic islands like Oahu. Basalt is a type of volcanic rock that is rich in iron and magnesium and forms as lava cools rapidly. Over time, the continuous flow of water has carved out the rock, creating the waterfall.
Basalt
The rocks around Manoa Falls, like much of the Hawaiian Islands, are primarily composed of basalt. Basalt is a type of igneous rock that forms from the solidification of molten lava. Basalt is characterized by its dark color, fine-grained texture, and high iron and magnesium content. It is one of the most common rock types found in volcanic islands and is associated with volcanic eruptions.
The specific composition of the basalt rocks at Manoa Falls may vary somewhat, but in general, it consists of minerals such as plagioclase feldspar, pyroxene, and olivine. These minerals give basalt its characteristic dark color and texture. The rock may also contain small vesicles or holes, which are often the result of gas bubbles trapped in the lava as it cooled and solidified.
Basalt rocks are found throughout the Hawaiian Islands and are a significant part of the island's geology. They have been shaped over millions of years by volcanic activity and erosion, contributing to the unique landscapes and features of the islands, including waterfalls like Manoa Falls.
Activities
Follow the trail to the waterfall and send me answers to the following questions. You can answer these from the observation area and do not need to go beyond that for the answers.
1. Observe the rocks surrounding the waterfall – what color are these rocks and how coarse or fine is the texture
2. Do you see any vesicles in the rocks in the surrounding area? If so how big are they in diameter?
3. Predict what will happen to the geology of the area over time
4. Take a picture of yourself at the falls