The sand mass that lies north of Noosa is known as Cooloola. The Cooloola Sand Mass is fixed by the volcanic rocks that form Double Island Point. The northward flow of sand in the longshore drift accumulates behind this headland creating a long surf beach 50 kms long. From the beach the onshore winds have then created first a foredune at the back of the beach, then as the sand continues to accumulate, the wind then creates parallel longitudinal dunes trending SE-NW. Between the dunes the swales are irregular and some of them are deep enough to intercept the local watertable, resulting in swamps and lakes between the dunes.
Much of the sand movement that has created this sand mass, occurred during the last ice age when sea level was significantly lower. Huge supplies of sand were available and and the extensive sand mass was created. Since those ancient times, the gradual rise in sealevel has meant that the longitudinal dunes have been truncated, particularly beyond Double Island Point, as pictured.
The truncation of the ancient dunes in the background is spectacularly obvious. The structure of the dunes is revealed.
In the bay, the seasonal changes in sand flow are revealed. Storm seasons increase the flow of sand into this bay, as it moves around Double Island Point. Then the waves move the underwater sand banks towards the beach at the foot of the sand cliffs, during quieter weather. As the sand banks move, tidal currents break through the sand banks creating rips and channels: pushing sand in, or carrying it biack to deeper water. Compare this photo with the Google Earth image to the right, t see the major changes in the sand banks in this end of wide Bay.