EarthCache: Hōlei Sea Arch 2.0
The Sea Arch is located in the Volcanoes National Park
Official homepage: http://www.nps.gov/havo/index.htm
Park Maps: http://www.nps.gov/havo/planyourvisit/maps.htm
Sea arches, such as Hōlei Sea Arch at the end of Chain of Craters Road, can be found along a wide swath of the southern coastline of Hawai’i.
They are remnants of once-continuous sea cliffs, where lava has previously met the sea and added to the size of the island.
The moment that new lava cooled and turned to rock, however, it began to erode.
Immediately, the pulverizing powers of wind and water began to pound and fracture the cliffs.
The seas on the southern edge of Hawai’i are known for being rough and having a violent surf.
Ever so slowly, these eroding waves break apart and wear away the rock, sculpting sea caves into the cliff.
As the waves pound into these new sea caves, the water hits the back wall of the cave and refracts.
The force of the water bouncing off the back of then begins to erode the cave’s headland, over time, forming a sea arch.
However, the forces of erosion don’t stop once this beautiful sculpture is created.
Given enough time, the force of the waves will cause the remaining bridge to collapse,
leaving behind a pile of rocks known as a sea stack.
Though they may appear mighty and permanent, individual sea arches are an
ephemeral feature of the island’s constantly shifting coastline.
A sea arch is a natural rock formation that occurs along coastlines,
created by the erosive forces of waves. Here’s how they form:
Formation Process:
1. Erosion of Rock: Sea arches typically form in areas where there are cliffs made of relatively soft rock, which can be eroded by wave action. The constant pounding of waves against the rock wears it away over time.
2. Formation of Caves: As waves continue to erode the base of the cliffs, they can create sea caves. This is often where the rock is weakest, such as at joints or fractures.
3. Further Erosion: Eventually, the cave may be eroded all the way through the rock, creating an opening that allows water to flow through. This can happen from both sides of the cliff.
4. Creation of the Arch: As the cave enlarges, it can form a bridge-like structure known as a sea arch. The top of the arch remains intact while the sides are eroded by the waves.
5. Collapse: Over time, if the arch continues to erode and loses structural integrity, it may eventually collapse, leaving behind a sea stack (a vertical column of rock).
Sea Arch:
Sea Arches are formed when a cave continues to be eroded and expanded until it cuts right through a headland.
Sea Stack:
A sea Stack forms when a sea arch continues to be eroded and widened until the rock becomes too weak to support the roof of the sea arch and collapses into the sea. The remaining pillar of rock is known as a sea stack.
Sea Stump:
A sea stump is formed when a tall sea stack is eroded and worn down until it juts just above the surface of the sea.
To log the cache please send me a message via the Message Center:
1. Date / time of visit:
2. Who was with you?
3. What were the wind and surf conditions and how do they affect the sea arch?
4. Take a closer look at the Sea Arch. What do you think?
a) Will it be able to withstand many more years of erosion before it collapses?
b) Do you think the roof will collapse or will the pillar give way to erosion first?
5) Why do you think the old lookout has been closed and moved further back?
6. If you look along the coast you can see several caves. Do you think more sea arches will form here in the next thousand years? Why do you think so?
7. Estimate the height of the sea arch?
You can also use Google to help you.
8. As of June 2019, earthcaches now contain required photo logging tasks. Please provide a photo of yourself, your GPSr, or a personal item with the Sea Arch that proves that you have visited this site. You can put this in your log.
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