New Zealand straddles the juncture of the Indo-Australian and Pacific
tectonic plates, two of Earth's major crustal plates. The two plates
generally converge in subduction zones, but in a scissor-like pattern,
with the Indo-Austalian plate overriding the Pacific plate to the north
and the Pacific plate overriding the Indo-Australian plate to the south.
New Zealand is "what happens" in between at and near the cross point of
this scissor pattern. Here the convergence has built two major islands
that together exhibit very active volcanoes and fault systems, and these
geologic features are very evident in the topographic pattern.
The North Island lies at the southern end of the west-over-east
(Indo-Australian over Pacific) plate convergence. The Pacific plate dives
under the North Island and this subduction process leads to melting of
rocks at depth, the rise of magma to the surface, and the formation of
volcanoes and other geothermal features. Most notable are Mount Taranaki on
the west coast, and Mounts Ruapehu, Ngauruhoe, and Tongariro just south
of the island's centerpoint, all of which are shown with white peaks in
this display. The Rotorua geothermal field occurs further northeast and
is evident here as a scattering of comparatively small bumps created by
smaller volcanic eruptions.
The South Island straddles the cross point of the subduction scissor
pattern and prominently features a fault system that connects the two
subduction zones. (The east-over-west (Pacific over Indo-Australian)
plate convergence generally occurs south of the South Island.) The Alpine
fault is the major strand of this fault system along most of the length
of the island, near and generally paralleling the west coast. Its impact
upon the topography is unmistakable, forming an extremely sharp and
straight northwest boundary to New Zealand's tallest mountains, the
Southern Alps. Although offsets on the Alpine fault are generally
right-lateral (35-40 millimeters per year) and thus consistent with the
offset in the subduction zone pattern, vertical offsets (about 7
millimeters per year) are likewise consistent with the uplift of the
Southern Alps.
Two visualization methods were combined to produce this image: shading
and color coding of topographic height. The shade image was derived by
computing topographic slope in the northwest-southeast direction, so that
northwest slopes appear bright and southeast slopes appear dark. Color
coding is directly related to topographic height, with green at the lower
elevations, rising through yellow and tan, to white at the highest
elevations.
Elevation data used in this image were acquired by the Shuttle Radar
Topography Mission aboard the Space Shuttle Endeavour, launched on Feb.
11, 2000. SRTM used the same radar instrument that comprised the
Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR)
that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed
to collect 3-D measurements of the Earth's surface. To collect the 3-D
data, engineers added a 60-meter (approximately 200-foot) mast, installed
additional C-band and X-band antennas, and improved tracking and
navigation devices. The mission is a cooperative project between NASA,
the National Geospatial-Intelligence Agency (NGA) of the U.S. Department
of Defense and the German and Italian space agencies. It is managed by
NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth
Science Enterprise, Washington, D.C.
Location: 33.5 to 48 degrees South latitude, 165 to 180 degrees East longitude
Orientation: North toward the top, cylindrical projection
Image Data: Shaded and colored SRTM elevation model
Date Acquired: February 2000