Hawaii Volcanoes N.P. | GeologyVirtualTrips

HAWAII VOLCANOES NATIONAL PARK

FIELD TRIP STOP – THE BIG ISLAND OF HAWAII – THE ONLY ISLAND WITH ACTIVE VOLCANOES

LOCATION: Hawaiian Islands, Eastern Pacific Ocean

GEOLOGIC FEATURES: Lava flows (Aa and Pahoehoe): Lava Vents; Shield Volcanoes; Caldera; Crater;Hot Spot; Seamount

DESCRIPTION: The Hawaiian Island chain is unique in that the volcanoes are the product of a Hot Spot rather than a tectonic plate boundary. A Hot Spot is a place on Earth where magma is funneled upward through the Mantle and Crust due to a concentration of heat high enough to melt rock.

Melted rock has a lower density than solid rock, so magma continues to rise till it reaches the ocean floor. There, it spills out and builds up till it breaks the water surface as an island.

In addition to the vertical movement of magma to the surface, the Pacific Plate is moving northwest at a rate of several inches per year, similar to a conveyor belt. Consequently, islands of the Hawaiian Chain that are located to the northwest are progressively older than islands found to the southeast of the Chain. Also, since the youngest island, Hawaii, is the only island positioned directly over the Hotspot, it is the only island having active volcanoes! A future island in the Hawaiian Chain is presently forming underwater south of Hawaii. This seamount, called Loihi, will eventually break the surface waters and become the newest Hawaiian island.

Islands, their ages, and average distances from the Hot Spot are listed below (from northwest to southeast):

Kaui 5.6 – 3.8 mya 322 miles

Oahu 3.3 – 2.2 mya 214 miles

Molokai 1.8 – 1.3 mya 148 miles

Maui 1.3 – 0.8 mya 98 miles

Hawaii 0.7 – Present 0 miles

Islands in the chain found north of Kaui include the Midway Islands which are 27 myo and are located about 1500 miles from the island of Hawaii. In actuality, the chain of islands continues mainly underwater all the way to Alaska where they are referred to as the Emperor Seamounts.

The reason that islands get progressively smaller and eventually submerged the farther away one gets from the Hot Spot is that (a) rock cools and therefore gets denser (heavier) the further away from the heat source reducing its exposed surface area, and (b) increased exposure to the elements causes increased weathering and erosion over time.

The Hawaiian Islands Volcanic National Park is found in the big island of Hawaii. Mauna Loa is active today as is Kilauea volcano near its eastern flank which has been especially active over the past several decades. Mauna Kea and Kohala volcanoes, found to the north on the Island of Hawaii are dormant since they are no longer over the active Hot Spot.

So, Kilauea is the youngest (and southeasternmost) volcano on the big island of Hawaii. Topographically, Kilauea appears as a bulge on the southeastern flank of Mauna Loa. Modern research, however, suggests that Kilauea is not part of Mauna Loa, but is instead a separate volcano with its own “plumbing system.”

Presently, the Puu Oo volcanic cone, found along a fissure east of Kilauea’s main vent (Kilauea’s East Rift Zone) has been active from 1983 to April of 2018. Photos included below were taken in December of 2017 shortly before Puu Oo “calmed down” from its 35 year activity.

STUDENT QUESTIONS:

(1) Why do islands northwest of the big island of Hawaii get progressively smaller in surface area over time?

(2) Two types of lava are found in the Hawaiian Islands, namely Aa and Pahoehoe. Describe the characteristics of each lava type.

(3) Hawaiian lava is composed of the igneous rock called Basalt. What is it about basalt that prevents it from causing hugely explosive volcanic events and allows it to be examined closely by tourists?

(4) Using the data given above, calculate the average movement of the Pacific Plate above the Hot Spot over geologic time.

(5) CHALLENGE: Why is it that the Hawaiian islands don’t form a continuous exposed ridge of lava rather than islands formed over discreet periods of time?

(6) CHALLENGE: Why are the Hawaiian Islands particularly susceptible to attack by tsunamis?

SELECTED REFERENCES:

-National Park Service. Hawai’I Volcanoes – What’s Going On With The Volcanoes?. (Last Updated: 4/8/20.) Accessed on 4/9/20: https://www.nps.gov/havo/planyourvisit/lava2.htm

-National Park Service. Hawai’I – Geology and Volcanoes. (Last Updated: 8/22/19.) Accessed on 4/9/20: https://www.nps.gov/locations/hawaii/geology.htm

VIDEO LINK: Helicopter over Puu Oo cone of Kilauea: https://youtu.be/maUI1FpYb84

CROSS-SECTION DIAGRAM AND PHOTOS:

HAWAIIAN ISLANDS

Figure 1 - Cross-section of the Hawaiian Islands showing the ages of the major islands (in millions of years) and the distance of each from the big island of Hawaii.

Figure 2 - Mauna Kea, the highest peak in the state of Hawaii and the tallest volcano in the world, rising over 33,000 ft above the ocean floor. It is a dormant volcano having been shifted north of the Hot Spot present further south.

Figure 3 - Exposure of Aa lava along the Hawaiian shore.

Figure 4 - Pahoehoe lava flows from a recent eruption of the East Rift Zone of Kilauea Volcano. Photo from helicopter taken 12/25/17.

Figure 5 - Approaching Puu Oo cone on the flank of Kilauea's East Rift Zone. Photo from Helicopter (12/25/17).

Figure 6 - View of Puu Oo volcanic cone. Photo for Helicopter (12/25/17).

Figure 7 - Circling around Puu Oo we begin to see the red magma. (12/25/17)

Figure 8 - Close-up view of magma in Puu Oo vent. Photo from helicopter (12/25/17).

Figure 9 - Road along the southeast shore of the big island is cut off by recent flows of lava from Puu Oo. (12/25/17)

New land formed during outpouring of recent lava

Figure 10 - Changes to the shoreline occur as new lava causes the shoreline to expand seaward/ (12/25/17)

Figure 11 - Mauna Kea. Helicopter view. (12/25/17)

Figure 12 - Halemaumau crater within the larger Kilauea Caldera. Photo at Kilauea Visitor Center (12/25/17).

Figure 13 - Panoramic view of Halemaumau Crater (right) within the larger Kilauea Caldera. (12/25/17). About five months after this photo was taken, Halemaumau collapsed, doubling its diameter.

Figure 14 - View of Kilauea Caldera seen to the left of Halemaumau Crater. (12/25/17)

Figure 15 - Pahoehoe type of lava flow. This lava type is characterized by relatively thin flows (up to a few feet) of lava with a smooth, ropy surface. This lava initially moves slowly. A surface skin then forms to inhibit heat loss. Movement of lava beneath the skin causes the surface folding seen in the photo. Insulation of lava beneath the skin allows lava to travel relatively large distances due to its low viscosity.

Figure 16 - Aa type of lava flow. This lava type is characterized by thick flows of lava with a rough, jagged, spinose and clinkery surface. This lava initially moves fast and resultingly cools quickly causing it to become thick (viscous). Overall low viscosity throughout the flow causes the surface crust to be reincorporated into a relatively thick flow.

Figure 17 - A view of Halemaumau Crater as observed from The Volcano House restaurant.

Figure 18 - Black Sand Beach found just downdrift from where lava flows entered the sea. Hot lava entering the ocean will cause the formation of sand-sized particles which are subsequently carried by waves along the shoreline.

Figure 19 - Pahoehoe lava exposed at the Black Sand beach found along the south shore of the big island of Hawaii.