a. EPS concentrators deal in more than just lava; they can choose to study oceanic or atmospheric processes (like the water cycle) and how they impact the natural world. In Hawaii, EPS students observed the relationship between the solid earth (the Big Island) and the water cycle. When you look at a satellite image of the Big Island, you’ll notice distinct areas of green and brown. The northern tip of the island is Kohala Mountain, the oldest volcano on the island, which last erupted about 60,000 years ago. The eastern side receives very high precipitation (up to 450 cm/year) due to the northeast trade winds, while the eastern side is in a rain shadow (less than 25 cm/year). There is a clear difference between the eastern and western sides of Kohala, both in terms of topography and vegetation
b. 360 Video: 62, 63, 65; 360 Photo: 64—Alakahi Stream (Kohala Mountain) Following an off-roading adventure and misty hike, EPS students reached the Alakahi Stream on the upper elevations of the wet side of Kohala. Note the abundant vegetation, mist, and stream. The area is characterized by thick mud and sphagnum moss. However, there are no large trees. Why isn’t this place a rain forest? It is actually too wet for large trees—it’s too wet for their roots. The small building is a weather station, and the large pipe is part of a hand-dug canal system (the Kohala ditch) that transports freshwater to lower elevations. The area is characterized by thick mud and sphagnum moss. Here, students collected water samples to test for pH and silica content. The pH provides information about biologic activity, and the silica content reflects the degree of weathering in the surrounding rock.
c. 360 Video: 66—Waipi’o Valley Overlook The wet side of Kohala has incredibly deep gorges (some dropping thousands of feet), compared to the gentle slopes of the dry western side. The largest gorge is called Waipi’o valley. The drop in elevation from the overlook to the beach is about 850 feet. The valley floor is filled with about 120 m of sediment derived from the canyon walls. The valley floor is ideal for taro farming, but has been devastated by tsunami in the past due to its low elevation. Students paused at this overlook for lunch before a steep hike down to the beach
d. 360 Video: 68; 360 Photos 67, 69—Hi’ilawe Stream, Waipi’o Valley The streams (such as Alakahi Stream) that form on the highest elevations of Kohala mountain move over steep valley walls in dramatic waterfalls and run across the valley floor toward the ocean. Students again collected water samples and compared the silica content at the top of the mountain (Alakahi Stream) with the valley floor (Hi’ilawe Stream and Wailoa Stream). Although the physical distance traveled by the water wasn’t large (less than 10 km), the dramatic increase in silica reflected the rapid weathering taking place on the wet side of the island. The wet climate increases weathering and erosion, which results in the steep canyons and valley floors filled with sediment
e. 360 Video: 77; 360 Photo 70, 71, 72—Waipi’o Valley Beach Rain and moisture captured by the highlands of Kohala reaches the Pacific Ocean at the Waipi’o Valley Beach, where students obligingly collected additional water samples.
Figures 1-2: (With or without labels). The Big Island of Hawaii has some of the most dramatic precipitation gradients (differences in the amount of rainfall over a short distance) on Earth! Wet, heavily-vegetated areas are mostly on the eastern side of the island, and are green in satellite imagery.
Figure 3: EPS concentrator Katie Polik poses for a photo as the fog momentarily clears on the top of Kohala, revealing the deep gorges and waterfalls below.
Figure 4: EPS secondary student Katie Gibson crosses the Alakahi Stream, which is darkened by high concentrations of organic material.
Figure 5: The breathtaking view from the Waipi’o Valley overlook, giving students a sense of how far down (and up!) they would be hiking to reach the valley floor.
Figure 6: A sign on the steep hike down to the Waipi’o Valley warns of tsunami danger. EPS concentrators may choose to study natural hazards and causes as they learn about Earth systems.
Figure 7 - 8: Several small streams cascade down the cliff walls and contribute to the Wailoa Stream that runs through the Waipi’o Valley.
Figure 9: Brave EPS students volunteer to jump into the Wailoa Stream in the Waipi’o Valley to collect water samples just before the river enters the Pacific Ocean.