Mr. Cleo: Honolulu's Future

Honolulu Hawaii is a beautiful place with many vast geological features. But now it is time to think of hat this beautiful place will be like in the near future! Now I will take you through space and time and give you a glimpse of Honolulu. Now gaze into my crystal ball…

Look closely, deeply focus, and I will take you there. 

1000 Years
Honululu has some awesome waterfalls that contribute to their beauty. But in a thousand years those waterfalls may or may not be there. The rainbow waterfall in Hawaii may not be there or be further pushed back. Waterfalls are commonly formed when a river is young. At these times the channel is often narrow and deep. When the river courses over resistant bedrock, erosion happens slowly, while downstream the erosion occurs more rapidly.

Visual explaining the process of waterfall formation. 

Rainbow Waterfall in Hawaii

As the watercourse increases its velocity at the edge of the waterfall, it plucks material from the riverbed. Whirlpools created in the turbulence as well as sand and stones carried by the watercourse increase the erosion capacity. This causes the waterfall to carve deeper into the bed and to recede upstream. Often over time, the waterfall will recede back to form a canyon or gorge downstream as it recedes upstream, and it will carve deeper into the ridge above it. The rate of retreat for a waterfall can be as
high as one and half meters per year. Often, the rock stratum just below the more resistant shelf will be of a softer type, meaning that undercutting due to splash back will occur here to form a shallow cave-like formation known as a rock shelter under and behind the waterfall. Eventually, the outcropping, more resistant cap rock will collapse under pressure to add blocks of rock to the base of the waterfall. These blocks of rock are then broken down into smaller boulders by attrition as they collide with each other, and they also erode the base of the waterfall by abrasion, creating a deep plunge pool or gorge.

Video explaining the formation of waterfalls for a better understanding of why waterfalls recede. 

10,000 Years
Sea levels have been rising all over the globe, but if they continue Honolulu and most of the Hawaiian islands are in trouble. By Sea level rising it will cause coastal flooding and ground water to rise as well. The freshwater body is less dense than the salt water and it floats on the salt water but as soon the sea level rises, the freshwater level will rise as well.

Video visual of what would happen if sea levels rise. 

Though average erosion rates are relatively low, perhaps a few inches per year, they range up to several feet per year and are highly variable from island to island however in 10 thousand years that will be a significant amount and Honolulu maybe underwater.


1,000,000 Years
In a million years I predict Nihoa, a little island not far from Honolulu will become an atoll. Corals begin to settle and grow around an oceanic island forming a fringing reef. It can take as long as 10,000 years for a fringing reef to form.

Picture showing the Atoll formation.

 Over the next 100,000 years, if conditions are favorable, the reef will continue to expand. As the reef expands, the interior island usually begins to subside and the fringing reef turns into a barrier reef. When the island completely subsides beneath the water leaving a ring of growing coral with an open lagoon in its center, it is called an atoll. The process of atoll formation may take as long as 30,000,000 years to occur.

Video showing and explaining how an atoll forms. 

Sources:
Notes
Casey Allen
http://www.eoearth.org/article/Atoll
http://www.worldwaterfalldatabase.com/
http://geography.howstuffworks.com/terms-and-associations/waterfall1.htm
http://www.epa.gov/climatestudents/impacts/signs/sea-level.html
http://www.soest.hawaii.edu/coasts/sealevel/