Indonesia is in one of the most seismically active regions on the planet and this week, Indonesians got two terrifying reminders of that fact. Twin natural disasters have hit the southeast Asian nation. More than 20 people were killed when Indonesia's most volatile volcano erupted in central Java. Also this week, a powerful earthquake off Sumatra island triggered a tsunami. The giant wave killed more than 270 people and left 400 missing. We get the latest from the BBC's Karishma Vaswani in Jakarta.