The blessings of volcanoes
that have nurtured life

15-million-year-old tree

The Silicified Wood of Nima

On the wave-cut platform of the Nima coast, where you can see the vivid green tuff, two large tree fossils (silicified wood) lie exposed. They have been designated as natural monuments of the prefecture under the name “The Silicified Wood of Nima.” If you look closely at the silicified wood lying on the wave-cut platform, you will notice veins of small, tightly packed quartz crystals running through the cracks. Quartz is a mineral made up of silicon dioxide, and this component is what turned the trees into stone.

More than 15 million years ago, the trees were buried in volcanic ash. Hot spring water then seeped into the wood and silicon dioxide that had been dissolved in the water solidified inside the trees, turning them into hard rocks. Although they retain the appearance of trees, their components have been almost entirely replaced, and they are now masses of silicon dioxide minerals such as quartz and agate.

1Wave-cut platform: This is a flat platform formed near sea level due to the erosion of coastal bedrock by the action of the waves. It is also known as a coastal bench. Along the Nima Coast between Nima Port and Kotogahama Beach stretches a relatively wide wave-cut platform. Here you can see formations of pyroclastic flows, volcanic ash, pyroclastic dikes, and agate veins created by volcanic activity over 15 million years ago.
2Quartz and agate: Quartz and agate are both minerals made of silicon dioxide, but while quartz comprises a single large crystal, agate is an aggregate of microscopic crystals. Opal is also another silicon dioxide mineral that contains a small amount of water. Silicified wood is mainly made of these three minerals.