Surfing on deep time

Vaitarna is a little river which arises in the Sahyadris and drains into the sea just north of Mumbai. It has been called India’s most polluted river, at least in the lower stretches. The upper parts have been called the most dammed river in India. This stretch is clean enough to supply drinking water to tens of millions. The 154 kilometer long river has three dams, which, between them, hold nearly a billion cubic meters of water. Why so many dams, I wondered as we walked along the uppermost of these dams.

The answer lies in the weather and the land. The Indian Ocean monsoon dumps incredible amounts of water on this land for three months every year. It has done that for tens of million years. The land itself was formed in the volcanic eruptions sixty to seventy million years ago, during the time that the dinosaurs died. The ancient lava flow cooled into the basalt of the Deccan Traps. Later it was weathered in the hot house that the earth became thirty million years ago. The weathering formed the thin red laterite soil that covers the Sahyadris. The deep channels eroded into the volcanic basalt channels the seasonal waters as they flow into the sea. The dams catch and store the rains.

This beautiful landscape is the shadow of incredible volcanic eruptions. The soil is thin, because the rain washes it away. Where it collects in deep trenches, agriculture is possible. Around the dams rich agriculture has developed in the last hundred years. You look at this land and see few trees. The highest growths are usually tall shrubs. The thin soil of the highlands is covered by low herbs, creepers, and grasses. Weird new species have evolved in the thin metallic soil. It is an amazing place for wildflowers and strange animals. The harsh land has given refuge to some hardy exotics.

Among them you may count the water spinach (Ipomoea aquatica). Although the locals do not seem to know it, it is edible. In this it is like many other morning glories in the genus Ipomoea. I’ve eaten its leaves both steamed and stir fried in my travels across Asia. It is hardy, grows in poor soil, and is a sure indicator of the presence of water. It needs little effort to cultivate. You just have to harvest it and eat it. I see it being used as a hardy decorative around the country. Why doesn’t anyone here eat it? Perhaps just the lack of knowledge about how edible it is.

The greening of a rock

At a place called Urulanthanni near Thattekad is a rock poking out of the surrounding rain forest. The area is a ecological hot spot. The dense canopy of the forest holds a very large variety of endemic birds, which are invisible from the ground. The rock provides a great vantage point from which to view the activity in the canopy. In fact, as you can see in the featured photo, the canopy itself is a grand view.

While walking in the forest I’d noticed basaltic rocks poking out of the ground at various places. So the whole rain forest here has been formed by sedimentation and erosion of the volcanic rock. This knoll that I stood on was a rougher rock. On the surface I could see a flowing texture created by weathering. You can see this in the photo below. But when I looked at a broken face in the rock, as in the photo above, I could see the grainy texture of the rock. It seems that the rock here is a mixture of two kinds called gabbro and syenite. Both have this texture, but are different in the minerals that they contain. So this giant rock must have been created by a separate upwelling of magma within the volcanic rocks underlying the land around us. The red insect is the nymph of a bug which I saw later.

How did inhospitable rock become the bed of a rain forest? Observations on Mount Saint Helens has given us a wonderful insight into how biology covers geology. Could I see the beginnings of the cycle on this dome? Almost certainly the bare rock was covered by bacteria. But the smallest things I could see were mosses. I regretted not bringing my macro attachment. I would have got wonderful photos here. At the next level of organization, I could see soil blown into little hollows in the rock, as in the photo above. Was this enough to support plants?

It seemed that it was. I could see clumps of bushes growing in these thin mats of soil. As they grow and shed leaves they add to the soil. They also present a barrier to winds which cause the air to drop soil around them. Right at the exposed top, the process of bootstrapping the creation of soil is slow. But just behind the flat top, it proceeds faster, accelerating even more as you go down the slope. In the photo above you can see the scant bushes at the flat top growing in a thin mat of soil, and the larger thickets of bush lower down. You can also see a few trees which have taken root in the upper slopes. Eventually, the bacteria, moss, bushes and trees will erode the stone into soil, and this dome will be covered in vegetation!

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