|
The
pacific plate, one of twelve huge, floating pieces of the earth's
crust, is always moving. In fact, it is now known (partly due to
research conducted on Haleakala) that the pacific plate is moving
northwestward at about four inches per year.
Most of the time, volcanoes are found on the edges of the plate where
all the action is, but sometimes there is what is known as a "hot
spot" in the earth's mantle or lower layer lying beneath the
plate. The mantle is hot enough in these locations to melt through the
earth's crust in places, and it does just that, creating a chain of
volcanoes as the plate slowly moves along. Haleakala is just one of
many such volcanoes.
Some
islands in the Hawaiian chain are older (Kaua'i and O'ahu, to name a
few) and a couple are younger (Hawai`i, which is still forming since
it continues to reside over a "hot spot", along with Loihi
Sea Mount, an actively forming undersea island-to-be about thirty
miles southeast of Hawai`i), but there is no doubt that the island of
Maui has many siblings. One-hundred-and-thirty-one (131) islands make
up the Hawaiian archipelago, spanning a distance of over fifteen
hundred miles; from Hawai`i; the most southeasterly island, to Midway
Island and Kure Atoll, located at the far northwestern reaches of the
chain.
The
volcano that formed East Maui emerged from the sea approximately one
million years ago. What is now known as the West Maui mountains was
already a large shield volcano by that time. It had stopped erupting
for the most part and had passed on it's "hot spot" to the
newly forming Haleakala. Frequent eruptions continued for another
half-million years, resulting in a mountain that rose much higher than
today's elevation of 10,023 feet. It is said that Haleakala would have
looked much as Mauna Loa on the Big Island looks today....a gently
sloping shield volcano of about 13,000 feet or so in elevation. For
thousands of years, erosion of all kinds....stream, wind, and some
even suggest glHTIal...cut valleys and gorges into the malleable land
mass.
Two
of the largest were the Ke'anae and Kaupo valleys, located on opposite
sides of the volcano. Slowly but surely these amphitheatre-headed
valleys carved their way towards the summit, finally merging to create
a large basin, and effectively removed several thousand feet of
elevation in their joining.
As
time passed, occasional eruptions spilled lava into the basin, leaving
behind vents, or "cinder cones", through which the lava
passed, helping to create the multi-hued "crater" that
visitors marvel at today.
The
geological history of the craters formation was disagreed upon for
quite some time, but the final verdict reminds us that Haleakala
"Crater" is not a crater in the true sense of the word. A
real crater would have been formed by either explosion (like Mt. St.
Helen's) or collapse, and while it is possible that some of the basin
was formed due to collapse (sinking into the earth's crust over time
due to the immense weight of the mountain), no one can be sure since
it is evident that so much of it was formed by erosion. Regardless of
the percentages, Haleakala's "mountaintop depression" is
truly a beautiful sight and one that will remain in any visitor's
memory for a long time.
The
sheer size of Haleakala is awe-inspiring. While 10,023 feet rises
above the warm sub-tropical seas, an amazing 28,000 feet lies below
the ocean's depths. Haleakala's diameter above sea level is 33 miles,
but no one knows the exact diameter of the base on the ocean floor.
These two measurements are why you will hear claims of Haleakala being
one of the biggest mountains in the world; it's just that, like most
of us, the vast majority of The House of the Sun's strength lies
hidden.
Today,
Haleakala is considered an "active" volcano, according to
sources at Hawai`i Volcanoes Observatory. Remember though,
"active" is a relative term. Most people think of a
currently erupting volcano when they hear the term "active",
but to volcanologists this isn't necessarily so. The last eruption was
in the late 1700's....about two hundred years ago. Geologically, this
is like yesterday's news, but Haleakala has been quiet for quite some
time, "humanly" speaking.
|
