Toba caldera and the remains of ancient super-eruptions

Further reading

Geologische overzichtskaart van den Nederlandsch Oost-Indischen archipel (Noord-Sumatra) Weltevreden:  Landsdrukkerij, 1919.

‘The Toba Depression', http://www.rpi.edu/~warkd/toba/toba_geology.html.

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