At about 10 miles, the road
descends the steep slope to the Hilina Pali Fault System. Holei
Pali is in the distance.
The diagram below shows the
geological explanation for the extremely steep terrain here.
This steep slope is a fault scarp. Rocks of the coastal region
have been down dropped about 1,000 feet relative to rocks higher
up on the flank of Kilauea. This movement occurs gradually over
a long period of time. For example, during the magnitude 7.2
earthquake in 1975, the largest earthquake in Hawaii this century,
a fault on the south flank of the volcano moved 5 feet.
 The
south flank of Kilauea volcano is being pushed towards the ocean
by the injection of magma into the rift zone. Volcanologists
use the Global Positioning System (GPS) to make precise measurements
of different locations on the volcano. GPS uses radio signals
from satellites to determine the location of a receiving station
to less than a centimeter. Measurements are made a few times
each year. The maximum rate of movement measured so far is 4
inches (10 cm) per year. This is a high rate of motion for a
geologic feature.
 The
mobile south flank of Kilauea volcano is part of a giant landslide
that extends 25 miles offshore. This slow moving landslide is
called the Hilina slump. The Hilina slump moves intermittently
over long periods of time. Other giant landslides in Hawaii
move catastrophically, removing large pieces of an island almost
instantaneously.
 The
fault scarps are draped in many places by pahoehoe and a'a lava
flows. Spectacular examples of these two types of lava can be
seen from the road. The transition from pahoehoe to a'a lava
is favored if the viscosity (stickiness) of the flow increases
(by cooling or the growth of more crystals) or if the shear
strain (how fast the interior of the flow is moving) increases
(by an increase in velocity of the flow or movement down a steep
slope).
Chain of Craters Road reaches
the base of Holei Pali and continues east on lava flows that
slope gently towards the ocean.
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