"Ngarai" (the Indonesia for canyon) Sianok lies at the outskirt of Bukittinggi. It is steep-canyon of about 100-150 meters high, very colorful and surrounded by a green valley with a winding river at its bottom. The beauty of this panoramic landscape is hard to describe as if no words can precisely express this geological wonder.
The ignimbtrite plato of Sianok Valley at Belakangbalok Village was produced by two periods of Maninjau volcanic eruptions.
The two eruption periods are separated by fluvio volcanic deposits, consisting of very qoarse sand and conglomerate.
The two periods pyroclatic deposits at containing pumice and locally several coal. These pyroclatic deposits were faulted and formed terrace morphology. The Sianok Valley is considered as an effect of the reactivation of basement fault throughting the ignimbrite deposits.
The ignimbtrite plato of Sianok Valley at Belakangbalok Village was produced by two periods of Maninjau volcanic eruptions.
The two eruption periods are separated by fluvio volcanic deposits, consisting of very qoarse sand and conglomerate.
The two periods pyroclatic deposits at containing pumice and locally several coal. These pyroclatic deposits were faulted and formed terrace morphology. The Sianok Valley is considered as an effect of the reactivation of basement fault throughting the ignimbrite deposits.
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