1.4 Volcanoes

From 164 to 140 million years ago, in the jurassic period, the area was shaken by numerous highly explosive volcanic eruptions. Sometimes tens of cubic kilometers of molten rock were blasted out in a single eruption.

Ground-hugging ash clouds then blanketed vast areas with hot ash.

Within the eruption crater the ash cooled slowly, forming tall, six-sided columns of rock such as those seen today on the Nine Pin Islands and at High Island Reservoir.

Rocks formed from ash and lava make up around 50 per cent of Hong Kong.

Molten rock that was not erupted to the surface cooled slowly at depth to form large bodies of granite. Uplift and erosion have exposed these coarse-grained rocks across 30 per cent of Hong Kong.

Credit : History Museum of HK.