Earth Science: Geology, the Environment, and the Universe

Chapter 20: Mountain Building

Problem of the Week

Up From the Deep

First, students must determine the age of Loihi.

There is more than one way to answer the problem above. It is important that students think and work through the information logically to come to a reasonable estimate/answer based on the given information.

Here's one way to do it:

1. One piece of the puzzle will be the age of the new volcano. Based on the information in the introduction:
   • Based on the discussion of volcano formation of underwater volcanoes like Loihi, Loihi’s age could be approximated to be about 200,000 years old.
   
   


2. Once the age is known, and knowing the height of the volcano (3000 meters), students can determine the average rate of growth per year:
   • 3000 m ÷ 200,000 y = 0.015 m/y or 1.5 cm/y
   
   


3. Then students can use this information to estimate how long it will be before Loihi breaks the surface:
   • 969 m ÷ 1.5 cm/y = 96,900 cm ÷ 1.5 cm/y = 64,600 years
   
   


4. Finally, given the estimated rate of plate movement (7.62 cm per year to the west-northwest relative to the Hawaiian hot spot) students can calculate how far the young volcano would travel in 64,600 years.
   • 7.62 cm/y × 64,600 y = 492,252 cm = 4922.52 m = 4.92252 km
   
   

**According to these estimates, Loihi will have moved only about 4.9 kilometers. Considering that Kilauea is 30 km to the northwest and has active volcanoes, then it is most likely that this new volcano in the Hawaiian chain will become the newest island, too.

And here is another way:

If there are 100,000 years until the volcano reaches the explosive phase, as it reaches a few feet from the surface, students could calculate the distance the volcano would move during these 100,000 years.

• 100,000 y × 7.62 cm/y = 760,000cm = 7,620m = 7.62 km


• Again, it is quite possible that Loihi will become the next island in the chain.

Resources:

1. http://www.soest.hawaii.edu/GG/HCV/haw_volc.html
   Great map showing islands, including Loihi, and their principle volcanoes.


2. http://www.soest.hawaii.edu/GG/HCV/hawaiispot.html
   Shows a graphic, not to scale, representation of the magma resources for Loihi, Kilauea, and Mauna Loa volcanoes.

References:

1. USGS Hawaiian Volcano Observatory


2. Hawaii Center for Volcanology


3. Hawaiian Volcano Observatory