When plate meets ring

Once upon a midnight in the 90s, I woke up when my parents and brothers suddenly left our house. With half consciousness, I closed the door, locked it then walked back to my bed. A few minutes later, my mom knocked the window and shouted “Wake up! Get out of the house!” I went out, saw some people were already on the street and still felt earthquake tremor. Since this incident, I used to experience some happening earthquakes in Sumatra and Java, while nicely sleeping or even doing a linear algebra exam in a class.

Earthquake often happens in my homeland, Indonesia (IDN). National Agency for Meteorology, Climatology and Geophysics recorded these phenomena 40 times only in October 2010. IDN is a meeting point of several tectonic plates, located between two continental plates: the Eurasian Plate and Australian Plate; and between two oceanic plates: the Indian Plate and Pacific Plate.  These plates move in relation to one another and frequently make collisions. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries. The lateral relative movement of the plates varies, though it is typically 0–100 mm annually.  Earthquake epicentre on sea can trigger tidal wave called tsunami.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Moreover, have you known about Pacific Ring of Fire? This ring is an area where large numbers of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean. IDN has about 150 volcanoes across its archipelago. These volcanoes are among the most active of the Pacific Ring of Fire. Some volcanoes are well-known for their eruptions. For instance, Lake Toba is the largest volcanic lake in the world. It is the site of a supervolcanic eruption that occurred 69,000-77,000 years ago, a massive climate-changing event which was responsible for six years of volcanic winter. In 1815 the eruption of Mount Tambora caused wide spread harvest failures in Northern Europe, the Northeastern United States, and eastern Canada, which was known as the Year Without a Summer. Mount Krakatau erupted in 1883, triggered huge tsunami and killed more than 35,000 people.

What about the present day?

In December 2004, an earthquake of the magnitude 9.3 shook Indian Ocean, west coast of Sumatra Island. Afterwards, severe tsunami occurred, swept North part of Sumatra and reached Sri Lanka, Bangladesh, India, Malaysia, Myanmar, Thailand, Singapore and the Maldives. Death toll was reported at around 220,000 people, most victims were Indonesian. If tsunami wave enters swallow water, it slows down but the amplitude increases. The wave hit everything in land, resulted swift flood flow mixed with debris of concrete materials. When visiting Banda Aceh in 2007, I saw a 200-ton ship on the land, 4 km away from seashore. It was stranded by the tsunami.

 

 

 

A 7.5 magnitude earthquake struck Mentawai Islands, West Sumatra province, on 25th October 2010.  Tsunami followed, 5 minutes after the earthquake, and hit the region which is one of the most famous surf destinations in the world. There are more than 400 deaths, about 23,000 displaced people and numbers of missing inhabitants. On the same day, the IDN government raised the alert of the nation’s most active volcano, Mount Merapi, to its highest level. The volcanoes started eruption by spewing lava, ash, gas and pyroclastic flow. Volcanic earthquake also increased. Pyroclastic flow, which can reach temperatures of about 1,000 °C and travel away at speed of 700 km/h, destroyed surrounding villages. Official reported there were 320,000 evacuated people and 194 death tolls. The highest alert level is still preserved today. Hundreds of volunteers (Red Cross, army, police, civilian, SAR, NGO) help to evacuate the local, seek corpses, and manage the evacuees. Hot ash on the ground forces the volunteers to use Hagglunds in the affected area of Mount Merapi. Yogyakarta airport remains closed and some national and international flights were canceled. Experiencing some natural disasters, IDN people must always be aware since the precise time of earthquake and volcano eruption is unpredictable.

May God save our beloved earth!

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