21 years ago today, a powerful 9.1 Magnitude earthquake struck off the coast of Sumatra, Indonesia, causing a catastrophic and deadly tsunami.

The earthquake, which lasted for an unrelenting 10 hours, ruptured a 900-mile fault line on the Indian-Australian tectonic plate boundary, causing the seafloor to rise by 40 metres, triggering the colossal tsunami.

Within 20 minutes, 100-foot waves had crashed into Banda Aceh, Indonesia, killing over 170,000 people and turning the city to rubble.

Over the next two hours, the tsunami sent 500 mph waves slamming into Thailand, India, and Sri Lanka, killing thousands more. After eight hours, deaths even occurred in South Africa after strong waves and swells caught swimmers by surprise.

Overall, nearly 230,000 people were killed in what remains one of the most-deadliest natural disasters in history.

The earthquake responsible for triggering the tsunami became the most powerful quake in the 21st century and the third-largest in recorded history.

Around £5.7 billion in aid was provided to the affected countries, raised by the Indonesian government, charity projects, private donors, and NGOs.

A tsunami is a natural disaster caused by earthquakes which hit at sea and cause a large displacement of water.

The name originates in Japan, a country which regularly sees tsunamis due to its position on the Ring of Fire. The tsunami of Boxing Day 2004 remains the worst instance in history.