Facts about Indonesian geography and natural disasters

Facts About Indonesia

This blog is the second in a series on facts about Indonesia. The first blog focused on Indonesian history, culture and religion and can be seen here. This one focuses on geography and details on a sample of the more devastating natural disasters that you may have heard of or will see during your visit to Indonesia.


Indonesia is the largest island nation in the world, located in South-East Asia and classified as an archipelago consisting of approximately 17,500 islands, of which 13,466 have been registered with the United Nations. Only one third of the islands are inhabited. The entire country measures 1,916,907 sq.km. and has coastline of 54,716 kilometers; surpassed only to Canada (243,042 km) and Norway (83.281 km). The islands can be broken into 4 groups: 1) the Greater Sunda Islands of Sumatra, Java, Sulawesi and the southern part of Kalimantan; 2) the Nusa Tenggara (Lesser Sunda) islands of Bali and a chain of islands that runs eastward through the island of Timor; 3) the Maluku islands; and 4) western part of the island of New Guinea.
map of Indonesia
The island of Java is 129,442 sq km and has a total population of 151,591,300, for a population density of 1,153 people per sq km. In comparison, New York State is 141,300 sq km and has a population of approximately 20,800,000 people for a population density of 147 people per sq km. Indonesia is classed as a tropical country sitting on the equator dividing the country between the northern hemisphere and the southern hemisphere. It has several of the largest rainforests in the world; the new Guinea Rainforest measures 288,000 sq km, the Borneo Rainforest is 220,00 sq km, and Sumatran Rainforest (home of the Orangutan) is 25,000 sq km. This last rainforest is estimated to be approximately 140 million years old, making it one of the oldest rainforests in the world.


Indonesia is located along the famous Ring of Fire, a horse shoe shaped belt of more than 850 to 1000 volcanoes which are located along the western coastline of South America all the way north along the western coast of the U.S. up to Alaska, across the Bering Strait to the Kamchatka Peninsula and down the eastern coast passing Japan, Korea, Taiwan, Hong Kong, Singapore, Thailand, Malaysia, Indonesia, then eastward to the Tonga Trench, Kermadec Trench and finally to New Zealand. The entire length of the Ring of Fire in approximately 25,000 kms (40,000 mi). Constant movement of tectonic plates occur along this ring, which cause collisions and create a nearly continuous series of subduction zones where volcanoes are created and earthquakes occur.
volcanoes, ring-of-fire
There are 147 volcanoes in Indonesia, 76 of them are active. Indonesia has had its fair share of volcanic eruptions in the past, the most famous of these are briefly described below.


Modern day Lake Toba in northern Sumatra is located inside a super-volcano. This lake is the product of an eruption 71 – 74,000 years ago that expelled 2,800 cu km (670 cu mi) of ash and lava into the atmosphere. Scientists believe that it was the largest volcanic eruption in all of human history, and some propose that it started a severe ice age that almost wiped out all of humanity. Temperatures worldwide plummeted by 3-5 degree C (5.4-9.0 degrees F) for many years after the explosion. The resultant explosion left a caldera 500 meters (1,640 ft) deep, 100 km (62.1 mi) long and 30 km (18.6 mi) wide.


In April 1815 a devastating volcanic eruption came from Mount Tambora on the island of Sumbawa. This eruption sent 160 to 213 cu km (38 to 51 cu mi) of material into the atmosphere. Steam and small eruptions continued in this volcano for the next 6 months to 3 years afterward. The ash reached 43 kms into the stratosphere and circled the world dropping world temperatures around the globe causing significant crop failures and triggering extreme weather conditions. 1816 became known as the year without a summer. The caldera is 6 km (3.7 mi) in diameter and 1,100 m (3,609 ft) deep. The caldera was formed after the estimated 4,000 m (13,123 ft) high peak was removed.
mount tambora volcano sumbawa
The sounds of recurring eruptions was heard as far away as Sumatra, 2,600 kms (1,600 mi) away, and ash fell 1,300 kms (810 mi) away. The caldera left behind was 6 to 7 kms (3.7 to 4.3 mi) across and 600 to 700 meters (2,000 to 2,300 ft) deep. It is estimated that around 11,000 people died and thousands were injured, and another 49,00 died of famine and epidemic diseases.


Another famous eruption came from the Krakatoa Volcano on May 20,1883. This volcano was 800 m (2625 ft) tall and was located between the islands of Sumatra and Java. The eruption sent shock waves around the world seven times and ruptured the eardrums of people over 64 km (40 miles) away. The eruption was about 13,000 times the nuclear yield of the Little Boy bomb that destroyed Hiroshima in Japan. Approximately 25 cu km (cu miles) of rock was blasted into the air, ash and smoke rose almost 11.3 km (7 mi) into the sky, and spread out over Sumatera and Java for 443 km (275 mi). The sound was heard to the west 4,780 km (2,970 mi) away on the island of Rodrigues near Mauritius, and also in Perth Australia and in Sri Lanka. Rumbling and minor eruptions continue for the next 3 months.
Krakatoa VolcanoSource: Library of Congress
Krakatoa erupted as well on 20 May and on 26 August, and with each eruption came devastating tsunamis. When the volcano collapsed into the ocean, a tidal wave 36.5 m (120 ft) high, that destroyed 165 villages in Southern Sumatera and Northern Java. At least 36,417 people died and many thousands injured because of the eruption and the resulting tsunami. There was so much debris in the atmosphere, it caused the earth’s temperature to drop 1.2 degrees Celsius, increased the incidence of violent storms and caused extensive crop failures around the world, thus affecting world food supplies. Sunsets were fiery red for 3 years afterward.


On 22 December 2018 the Anak Krakatoa erupted and one side of the volcano collapsed into the sea and causing a submarine land that created a 13-meter-high tsunami that killed 437 people. This tsunami came 3 months after the 2018 Sulawesi tsunami which killed approximately 2000 lives.
anak krakatoa volcanoSource: Elsevier Ocean Engineering Volum1 195, 1 January 2020
The volcano erupted again on 10 April 2020 creating two plumes of ash and smoke 14 km (46,000 ft) and another to 11 km (36,000 ft). The eruption only caused lava flows and no major damage was reported for this eruption which only lasted several hours.


Mount Agung is believed by the Balinese to be a fragment of the holy Mountain Meru. Mount Meru is a golden mountain believed to be the connection between heaven and earth, and the dwelling place of Hindu gods. It is also believed that fragments of the Meru Mountain are also identified with Mount Rinjani in Lombok, and Mount Bromo in Java to stabilize them spiritually.
mount agung volcano
Mount Agung is located in north-east Bali is 3,031 (9,944 ft) above sea level, and is the highest point in Bali. The volcano is an active volcano and has seen many eruptions over time. It has a long history of eruptions: 1808, 1821, 1843, 1963-64, 2017-19. In 1963 devastating eruptions occurred on 18 February, 14 February, and 17 March causing ash and rock 8 to 10 km into the air, and causing massive pyroclastic flows that destroyed many villages and killed an estimated 1,100 to 1,500 people. This was followed by minor eruptions that lasted for another year. The mother temple, Pura Besakih was not destroyed in the eruption, which is seen as a miracle and a sign from the gods. From November to September 2017 there were 844 minor earthquakes, the seismologists gave the alarm and 122,500 people were evacuated. In November 2017 volcanic activity increased again, erupting as ash cloud 3.8 km (2.4 mi) into the air. A week later there was another eruption spewing ash 9.1 km (5.6 mi) in the air, and causing a mud-pyroclastic flows that displaced 100,000 people in a 10-mile radius around the volcano. In June 2018 the volcano sent a 2 km (1.2 mi) plume into the air disrupting air traffic and causing delays. On 3 July 2018 another eruption sent lava and rocks in all directions, and in late May 2019 the volcano spewed ash, lava and rocks spread over 3 km (1.9 mi) and temporarily disrupting international flights.
Besakih hindu templeBesakih Hindu Temple
Each of the Hindu Temple has a Meru Tower with a multi-thatched roof to represent Mount Meru. This tower is located in the inner most part of the temple. This meru is seen as a ‘temporary resting place’ of the gods here on Earth. The number of tiers on the Meru Tower are dedicated to specific gods indicating their importance. Many meru towers are found in Pura Besakih, the most important temple in Bali, is found high up on the slopes of Mount Agung.


Mount Batur is another active volcano and is dated between 23,670 to 28,500 years ago. It is located northwest of the Mount Agung volcano and 30 km (19 mi) from the town of Ubud. This is a volcano within a volcano, and a Lake Batur has been formed as a result. This lake measures 15.9 sq km (3,900 acres) and is 88 m (289 ft) deep, and is a popular fishing spot. The outer caldera (bowl) measures 10 km x 13 km (6.2 mi x 8.1 mi) across. The inner caldera is 7.5 km (4.7 mi) across.
Mount Tabor and Mount Agung, Bali
The first documented eruption was in 1804, followed by activities in 1804, 1821, 1849, 1854, 1888, 1897, 1904, 1904, 1921, 1922, 1923, 1924, 1925, 1926, 1963-1964, 1965, 1966, 1968, 1970,1971, 1972, 1973, 1974, 1994, 1998, 1999-2000. In 1968 lava flowed from the volcano and can still be seen from Kintamani on the rim of the volcano, and in 1917 an eruption killed 1,372 people and destroyed 2,500 temples and 65,000 houses. As in Mount Agung, the lava stopped short of destroying the second most important temple in Bali, the Pura Ulun Danau Batur, which was seen as a miracle. Eruptions began on 12 March 1999, there were 6 small explosions on 17 May and anther on 25 May that caused ash and lave to spew out of the volcano. In 2000 there was another eruption on 22 March where ash and rock climbed 200 m above the volcano. These ash emissions continued until April 2000 and have since been quiet. Tourist activities resumed shortly after and they still run a 2-hour hike up and 1.5 hour hike down the volcano.
mount batur volcano bali
The volcano is believed to be the dwelling place of the god Lord Brahma, the creator of the world and all creatures, and Goddess Ida Bhatari Dewi Danu, the giver of life through the water from Lake Batur. This water is channeled throughout Bali as a source of water for extensive rice fields, and water for consumption.


Mount Bromo is one of the most scenic volcanoes in all of Indonesia. This stratovolcano volcano is 2,329 m (7,624 ft) at its summit and it dates back 820,000 years. A cluster of four volcanoes has formed in the last several thousand years in the 16 km wide caldera. Mount Bromo is the youngest of these volcanoes.
Mount Bromo, Java
This caldera has been designated the Bromo Tengger Semeru National Park and it is the only conservation area that has a sand sea, which is in fact a wind blown plain of fine sand (no water). It is a popular tourist destination. People stay in home stays and hotels along the rim and take early morning trips using horses, jeeps or just hiking to see the sunrise from the top of the volcano rim. Many also like to hike along the rim as the views are fantastic. The volcano has great cultural significance for the Tenggerese people in the region. On the 14th day of the Hindu festival of Yadnya Kasada, the people travel to the volcano to throw gifts of fruit, rice, vegetables, flowers and sacrifices of livestock into the crater. This practice started in the 15th century. At the base of Mount Bromo is the Hindu temple ‘Pura Luhur Poten’, where prayers and offerings of appreciation are made for the blessings and welfare they have received, and to ask for further blessings. The ceremony last for approximately one month. The temple is made for the Hindu god Sang Hyang Widhi also known as Brahma, the god of creation, and Mahadevi also known as Shiva. Mount Bromo has always been an active volcano. The earliest eruptions go back to September 1804, and up to December 2020 there have 62 other instances.


In additional frequent volcanic eruptions, there a number of tsunamis that hit Indonesia each year and information is provided below on the worst of these tsunamis.


The Indian Ocean earthquake and tsunami also called the Boxing Day Tsunami because it occurred at 7:58 a.m. in local time on 26 December, the day after Christmas. This tsunami was caused by a great underwater earthquake off the west coast of Sumatra, its strength measured 9.1 to 9.3 on the Richter Scale. It was so powerful it caused the entire earth to shake, and started other earthquakes as far away as Iceland. The earthquake was the third-largest ever recorded, the largest in the 21st century The tsunami caused heavy damage along the coasts in the Indian Ocean affecting Malaysia, Thailand, Maldives, Indonesia and Sri Lanka and parts of India. Tidal waves as high as 30 meters destroyed thousands of homes and killed over 230,000 people. The tidal wave traveled 7,558 km (4,096 mi) to distant Somalia in East Africa resulting in 312 people dead or missing.
tsunami Aceh December 2004A village near the coast of Sumatra lays in ruin after the Tsunami that struck South East Asia. U.S. Navy photo by Photographer’s Mate 2nd Class Philip A. McDaniel (RELEASED). Source: commons.wikipedia.org
The earthquake and resulting tsunami drew world attention and multiple countries and international, and local NGOs worked together with the Indonesian Government on a quick response for those affected. Approximately US$ 14 billion was used for the immediate response and the sustainable recovery operations which lasted for about 5 years. Additional information related to Indonesia can be found at these two blog sites: Beautiful Places to see in Indonesia, and Tropical Island Clothing- the clothes you choose for your vacation.   Please leave a comment if this blog was of use or interesting, and please provide suggestions for improvement should you have any. Your input is of great importance to me. Thank you!

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