Geology of New Zealand Field Trip Guidebook - ResearchGate

it, the melt water stream emerging from the snout, the character of the outwash sediments,
striations on the overhanging valley walls, and evidence of higher stands of the glacial ice,
especially lateral moraines. If the weather is good, you may be able to look up the glacier to
see the snow fields below Aoraki. Both Fox and Franz Josef glaciers extend down nearly to
sea level, while the glaciers on the east side of the Southern Alps are confined to high
elevations (recall the hike up to Hooker Glacier). While the temperatures on both sides of the
Alps are similar, precipitation patterns are not. The extension of west coast glaciers to lower
elevations reflects not cooler temperatures, but the greater supplies of winter snow delivered
to the western slopes. Recall the glacial budget we discussed in lecture. In what other ways
can you compare and contrast the Hooker and Fox glaciers?
Notebook Assignment: Make the observations mentioned above and describe them in your
notebook. Any other observations will garner higher marks.
Stop 4: Hare Mare Creek, Alpine Fault Exposure
The Alpine Fault is exposed 200 m up the creek in the south bank. We will walk up the north
bank to view the fault. Beanland [, 1987 #3] describes the exposure as mylonite thrust over
gravel. Mylonite is a fine-grained metamorphic rock that commonly has very fine banding of
different colors. Mylonite only occurs in shear zones like the Alpine Fault, where
tremendous amounts of stress are placed on the rocks right around the fault. This stress
causes minerals to reform and align in bands to essentially take up less space.
Notebook Assignment: Sketch this exposure, indicating the features that mark it as a fault
zone. This is about as close as you can get to seeing a boundary between two plates. Do you
notice any difference in the rocks on either side of the fault? As you consider the fault and
the transform boundary it represents, remember that there has been more than 450 km of slip
along this fault.
Day 5—Tuesday 18 November.
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Stop 1: Franz Josef Visitor Center
Our first stop this morning will be the Franz Josef Visitor Center. Take your notebook and
make some notes on two aspects of the local geology: 1) the Alpine Fault and the earthquake
hazards it presents, and 2) the historical record of ice advance and retreat for both the Franz
Josef and Fox glaciers. Also, be on the lookout for signs of the trace of the Alpine Fault. We
will cross it at some point between the Holiday Park and the glacier.
Stop 2: Waiho River Bridge and Franz Josef Glacier Access Road
The Waiho River drains the Franz Josef Glacier (with contributions from other streams) and
is considered a major flood risk by the New Zealand Ministry of Civil Defense and
Emergency Management. Below the canyon mouth (west of the highway bridge), the river is
partially constrained by the Waiho Loop, a recessional moraine that forms a prominent
forested ridge. Between the glacier front and this moraine, the riverbed is aggrading
(depositing sediment) with glacially derived sediment. Between 1940 and 2002 the river bed
rose by more than 10 meters, lifting it above adjacent areas and creating significant flood
risks. This risk is heightened by periods of glacial outburst—sudden, copious releases of
water from the glacier margin. As you stand by the river, compare the elevation of its bed to
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