Welcome to Lake Illawarra! This EarthCache will help you learn about barrier beaches and how they shape this beautiful coastal lake Get ready to explore and discover how these natural features protect and change over time
Formation of Barrier Beaches: Barrier beaches at Lake Illawarra form slowly over thousands of years. Waves and tides move sand and dirt along the shore, where it collects in quieter areas, like bays. Over time, these sandy deposits build up into long, narrow barriers that stretch across the coast. The shape and slope of these beaches depend on the size of the sand grains and how strong the waves are. Bigger grains make steeper beaches, while smaller grains make gentler slopes.
How Barrier Beaches Change: Barrier beaches are always changing because of nature and people. When sea levels rise, more water covers the coast, adding more sand and mud to the beaches. But when sea levels fall, the beaches can shrink or even disappear. Big storms, like cyclones, also reshape beaches by washing away sand or making new piles. People building houses and roads near the beach can change how the sand moves, too.
Barrier beach History of Lake Illawarra: Lake Illawarra has changed over thousands of years:
- First Stage: A big valley formed when sea levels were low.
- Rising Sea Levels (8000-7500 years ago): After the last ice age, the valley flooded, covering the floor with sand.
- Barrier and lake Formation (5000 years ago): As the barrier formed, a calm lake formed behind it, changing from open sea to a sheltered area.
- Sea Level Drop (3200-2500 years ago): Slight drops in sea levels made the ocean move less, leading to more sand and mud in the bay.
- Modern Changes (last 200 years): People have built cities and farms nearby, which has made more sand and mud go into the lake
Logging Tasks:
-
Observation: Observation: Describe the physical characteristics of the barrier beach you observe. Note the size, shape, and any visible signs of erosion or sediment deposition.
-
Consideration: How does the width of the barrier beach at Windang affect Lake Illawarra's connection to the sea in terms of water flow dynamics and sediment transport?"
-
Photograph: Take a photo with the barrier beach in the back to show you were there.
References:
- Geomorphology of Lake Illawarra barrier estuary - Mid Holocene: ResearchGate
- Lake Illawarra - Wikipedia
- Coastal Geomorphology: An Introduction by Bird, Eric C. F.
Logging Instructions: Log your find and send your answers to me in the next 10-14 days by email or GC Messenger. Don't put your answers in your public log