Orbital snaps reveal Roebuck Bay's tidal movements

March 1, 2016 by Geoff Vivian, Sciencenetwork Wa, Science Network WA
Orbital snaps reveal Roebuck Bay’s tidal movements
This photo of Roebuck Bay was taken from the International Space Station on June 11, 2015 using a Nikon D4 digital camera using an 1150 millimeter lens. Credit: Image courtesy of the Earth Science and Remote Sensing Unit, NASA Johnson Space Center

A photo of Roebuck Bay just south of Broome, snapped by a curious astronaut on the International Space Station, has called into question the origin of some of the region's highly-unusual parallel tidal creeks.

Tidal creeks in the Kimberley are formed by huge tides—in Broome the spring tide ebbs and flows more than nine metres in about 12 hours.

This completely submerges some of the mangrove trees which are adapted to growing in these conditions.

The aqua-blue area in this photograph shows Roebuck Bay seawater, and the margin of white between this and the dark green fringe of mangroves shows the tide is not completely in.

When the water floods relatively flat land, it forms substantial saltwater creeks when it flows rapidly out again, depositing salty white mud.

You can see this white mud between the mangroves and the aquamarine sea, and also in the empty creek bottoms.

These creeks typically take a meandering tree-like (or dendritic) form, like the creek system you can see the top of the pale area in this photograph.

This is in marked contrast to the roughly-parallel creeks which show up as white feathery structures on the left of the image, eleven of them penetrating the red soils and yellow-green pastures of Roebuck Plains Station.

UWA geologist Dr Karl-Heinz Wyrwoll agrees with NASA's interpretation of the feather-like formations, describing them as channels between former desert sand that were inundated when sea levels rose to their present height about seven thousand years ago.

However, geomorphologist Dr Ian Eliot says these would have been washed away when sea levels were approximately two metres higher than today.

He says the unusual parallel dunes are tidal channels formed by rapid water flows.

Both scientists refer to Google Earth images of country further inland to back up their assertions.

Dr Wyrwoll says similar dunes he has studied near Derby and the Fitzroy Valley have been active several times in the past 20,000 years, pointing to drier periods.

During these times the winds would have gradually moved the dunes as there was not enough covering vegetation to keep the sand stable.

The sea simply followed the pattern of these dunes in Roebuck Bay, the tides forming creeks as they flowed between the ridges, he says.

Both scientist agree that the sea has flooded larger parts of Roebuck Plains at some stage during the last few thousand years, obliterating the old desert dunes.

Explore further: Travelling dunes encroach on infrastructure, and reveal geological pattern

Related Stories

Image: Great Sandy Desert, Australia

April 9, 2013

(Phys.org) —In northwest Australia, the Great Sandy Desert holds great geological interest as a zone of active sand dune movement. While a variety of dune forms appear across the region, this astronaut photograph features ...

View from orbit of a huge white sands dust storm

May 1, 2012

It’s clear from this image of why a region in New Mexico, USA is called ‘White Sands.’ The dust plumes in this photograph taken by an astronaut on board the International Space Station show a dust storm in ...

Image: Martian sand dunes in spring

March 7, 2014

(Phys.org) —Mars' northern-most sand dunes are beginning to emerge from their winter cover of seasonal carbon dioxide (dry) ice. Dark, bare south-facing slopes are soaking up the warmth of the sun.

Recommended for you

Semimetals are high conductors

March 18, 2019

Researchers in China and at UC Davis have measured high conductivity in very thin layers of niobium arsenide, a type of material called a Weyl semimetal. The material has about three times the conductivity of copper at room ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.