 Bargara
and adjacent coastal areas lie on the western side of the wide mouth of Hervey Bay. Wave action is
generally low under south-easterly weather conditions, with the coastline here
is protected by Fraser Island. However, under north-easterlies (such as may occur
during cyclone season), wave action can be expected to be much greater.
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 Photo A:
Rocks rounded by wave action. The tumbling action to round these rocks is
greatest under high wave conditions.
Photo B: Under calm weather the Sail Training Ship Young Endeavour
lies at anchor during one of its voyages. This tall ship offers
adventure and training opportunities for young people through sail-based and
cooperative activities.
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STS 'Young Endeavour'
Photo 1A: Southern end of Mon Repos Beach,
a little north of Bargara
Photo 1B: Young Endeavour off Mon Repos Beach
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Bargara Beach illustrates
some interesting geomorphic features. The majority of rocks are rounded
and volcanic in origin. Two conclusions result from this; wave action
has tumbled and rounded these rocks, and there must have been a source of
lava nearby. Note that the colour of a rock on the surface (weathered) may be different
from that of the fresh rock face (unweathered).
One of the clues to identifying a rock as volcanic can be seen on the
photo inset (right). Holes are found throughout this rock, and many of the
others on the beach. They formed from gases in the original fluid magma, and
as
the material rose towards the surface, pressure release caused dissolved
gases to bubble out of solution. As this material cooled and solidified at the surface, many bubbles were trapped in the rock.
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Photo 2: Rounded rocks on north Bargara Beach |
Wave action on the beach has sorted rocks into different size
categories (study photo, above right). On the lower beach, are boulders,
above is a terrace of smaller rocks, and higher still, even smaller rocks form
another terrace. This reflects a reduction in the transporting power of waves as they travel
further up the beach.
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 Mon
Repos Conservation Park is significant for protection of marine reptiles.
If you study the signboard (photo, right) you should work out what type of
reptile visits this area.
These creatures come from the sea, crawling onto the beach sands to nest
above the water line. Eggs are laid in holes in the sand, and eventually the
young hatch and struggle to the water. It is necessary to control tourism
and real estate development along the beach, as artificial lights at night
can confuse the animals, and put them off course.
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Mon Repos Conservation Park
Photo 3: Conservation Park, behind Mon Repos Beach
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Visitors at nesting times must observe strict rules about the use of lights.
Note the specially constructed boardwalk lights, facing
downwards.
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The small creek shown emerges onto Mon Repos, flowing out from the marsh
behind the beach. The rocks and stones in the creek bed have been tumbled by
moving water. Layers of sand, granules and fine pebbles, through which the creek
has cut its channel, have built up on the beach.
Examination of the eroded 'cliff' cut into the sand reveals that the coarser
pebbles form a sloped surface, while the sand forms a vertical face. The
conclusion is that the pebbles, being larger and quite rounded, readily
slide past each other (especially when wet), causing more slipping than
the sand.
The eroded bank in the background contains small and large rounded rocks,
and shells.
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Photo 4: Creek mouth, Mon Repos Beach |
The
creek described above, on the southern end of Mon Repos Beach, spreads
outwards across the sandy beach. At low tide the flowing water moves and
sorts the sand into patterns that are reminiscent of rivers acting on a
larger scale. Erosion and deposition also take place on this small scale.
The photo (right) shows an area over which the stream has recently flowed.
When the water flow is strong, erosion cuts channels into the sand, and only
larger particles can be deposited (see photo). When the flow is gentle,
there is little erosion, with deposition filling in channels with finer
sediments (see photo). The photo may be interpreted as though the small
pebbles and granules were deposited first (by the stream or waves), then later the sand
was deposited (by the stream). The larger stones were probably moved by
waves at high tide.
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Photo 5: Sand
deposition at creek mouth, Mon Repos Beach
(Note: lens cap on left for scale, thus view is about one metre across)
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Imagine that this 'landscape' was at a larger scale (say, a hundred metres
across instead of one metre across). Sedimentary rocks are
characterised largely by the sediments making them up. After looking at this
scene it becomes clear how sedimentary rocks of different particle size can
form near each other, largely as a function of the depositional environment
and conditions of the time.
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The
Hummock is a low volcanic hill between Bargara (on the coast) and Bundaberg
(on the Burnett River floodplain). The area surrounding The Hummock has a high agricultural productivity, with sugar cane making up most of the
farmland. The land on either side of the river is made up of alluvial
soil. Closer to the Hummock, the red fields are derived from basalt (a rock
formed from cooling lava).
Photo A: Looking to the south-east,
fertile soils supporting cane fields give way near the coast to sandy soils.
Small resort towns dot the coastline.
Photo B: Bundaberg, on the Burnett River flood plain.
Photo C: Close to the river mouth, the sugar mill is located to
receive sugar cane from surrounding farm land, and to transport products out
by ship. Near the mouth of a major river, the flood plain is a wide, flat
area, built up over thousands of years as flood waters flow over the plain
and alluvium (mainly silt) settles, raising the plain a little each
time.
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The Hummock Lookout
Photo 6: View from the Hummock Lookout, Bundaberg-Bargara district
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Page
FLINDERS
THEME:
At the northern end of Hervey Bay
This district is at the northern edge of
Hervey Bay, which opens out at the northern end of the Great Sandy Strait,
discovered by Matthew Flinders in the Norfolk in 1799. He named an
extinct volcano, the only hill of this area 'Sloping Hummock', now called
'The Hummock'. Captain Flinders returned to this area in 1802 in the Investigator
while heading north on the
second phase of the great voyage of circumnavigation.
