A trip to Tam Hai, Quang Nam - typical volcanic terrain

 In August and September 2022, I have been Tam Hai for a couple of short trips.

Tam Hai is a small island off the coastal line in the central Vietnam with an area of approx. 15 square kilometers, surrounded by the blue sea. There is a small coral reef in the southeastern edge. To be honest, the scenery is not really impressive to me, however, the volcanic terrain in the sea cliff of Ban Than caught my attention.

I am quite familiar with the mountainous topography full of sedimentary rock like limestone, karst caves, beaches with sandstone in the north of Vietnam. When moving to central Vietnam, I learnt more about igneous mountains of granite. However volcanic terrain is still so new and attractive to me.

The formation of the volcanic terrain is really interesting. The site was once a volcano, then it exploded and erupted the molten lavas. Lavas rolled down the slope until reached the sea and cooled down to become solid and hard igneous rock.

In the cliff, I can see a spectacular scene of solid lavas, the latter wave covered the former one just like what we can see at the stand of a burning candle. In some intertidal zones, despite of both the erosion of the sea and the exposure to the weather, the solid lavas still look so new with shiny black color as if they were just formed yesterday. 

In some other areas, because of the impact of the weathering, rocks are broken in to blocks, showing surfaces full of pumice bubble textures. In some areas, I can see the rocks were formed into different layers with different colors, they question my knowledge. Are they original igneous rock or some type of sedimentary or metamorphic rocks?

There are also strange blocks of stone with red color separately lying in the shore. I guess that they consist high content of iron compositions, they were once formed contemporaneously with other rocks but after the time, while the other were washed away, they still remains.

To talk about the time, I haven't got the exact clue when the formation happened. But because of the geographical proximity, we can consider another famous island with volcanic terrain nearby - Ly Son island which is said to be formed from 25-30 million years ago. Of course, many more examinations should be carried out to identify what the materials are, but I think there are bases to say they are basalt rocks due to the appearance, origin and and again, the proximity to Lyson island.

There are so much to say and explore. I hope to have more chances to get back there for further examination.

Quangngai, November, 23rd, 2022