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Tengger Caldera

Java's Otherworldly Sea of Sand

Elevation

2,329 m

Last Eruption

2023

Type

Stratovolcano(es) / Caldera complex

Country

Indonesia

Location

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Volcanic Hazards & Risk Assessment

Primary Hazards

  • Pyroclastic flows and surges
  • Large explosive eruptions (VEI 4+)
  • Ash fall and tephra deposits
  • Lahars and debris flows
  • Pyroclastic flows
  • Lava flows
  • Volcanic bombs and ballistics
  • Lahars and mudflows

Risk Level

Population at RiskHigh
Infrastructure RiskHigh
Aviation RiskSignificant

Geological Composition & Structure

Rock Types

Primary
Unknown
Silica Content
Varied composition

Tectonic Setting

Unknown
Intraplate setting with hotspot or regional volcanic activity.

Age & Formation

Epoch
Unknown
Evidence
Unknown

Eruption Statistics & Analysis

MetricValueGlobal RankingSignificance
Total Recorded EruptionsUnknownLowModerately active volcano
Maximum VEIVEI UnknownMinorLocal impact potential
Recent Activity3 years agoVery RecentCurrently active

Monitoring & Alert Status

Monitoring Networks

Global Volcanism Program
International eruption database

Current Status

Active
Recent volcanic activity detected. Continuous monitoring in place.

Authority Sources

Smithsonian GVP
Official volcano database

Related Volcanoes

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East Java, Sunda Volcanic Arc
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brown and green mountain under white sky during daytime

kilarov

via Unsplash

brown mountains under white sky during daytime

kilarov

via Unsplash

green and brown mountains near body of water during daytime

kilarov

via Unsplash

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Interesting Facts

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Tengger Caldera's 'Sea of Sand' (Lautan Pasir) is a 9 × 10 km desert-like expanse of volcanic sand at 2,100 m elevation — one of the most surreal landscapes in tropical Indonesia.

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Mount Bromo is named after Brahma, the Hindu god of creation, reflecting the centuries-old Hindu traditions of the Tenggerese people.

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The annual Kasada ceremony involves Tenggerese Hindus throwing offerings of rice, livestock, and money into Bromo's active crater to appease the gods.

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The massive Tengger volcanic complex dates back approximately 820,000 years and includes five overlapping stratovolcanoes, each truncated by its own caldera.

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Bromo has erupted 72 times in recorded history, with activity in virtually every decade since 1804.

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The Penanjakan sunrise viewpoint (2,770 m) on the caldera rim offers one of the most iconic volcanic panoramas in the world, overlooking the caldera, cones, and distant Semeru.

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More than 500,000 tourists visit Tengger Caldera annually, making it one of Indonesia's most popular natural attractions.

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The ~830 BCE VEI 4 eruption was associated with a major phase of caldera formation, demonstrating the system's capacity for eruptions far larger than Bromo's typical activity.

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A concrete stairway of 253 steps leads from the Sea of Sand to Bromo's crater rim, allowing visitors to peer into the smoking vent.

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The Tenggerese are a Hindu minority of approximately 100,000 people living on the caldera rim, maintaining traditions predating the Islamization of Java.

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Bromo's eruptions are typically small (VEI 1–2) phreatic or phreatomagmatic events, producing ash plumes and steam rather than lava flows.

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Approximately 800,000 people live within 30 km of the caldera, primarily in agricultural communities growing vegetables and flowers on the fertile volcanic slopes.

Frequently Asked Questions

Is Mount Bromo still active?
Yes, Mount Bromo is one of the most active volcanic vents in Java. It last erupted on December 13, 2023, and has produced eruptions in 2019, 2020, 2021, and 2023 in recent years alone. The volcano averages roughly one eruption every 2–4 years, though these are typically small (VEI 1–2) phreatic or phreatomagmatic events. Bromo's crater continuously emits sulfurous gases and steam, and the volcano is monitored by CVGHM with seismometers and webcams. Larger VEI 3 eruptions occur less frequently but have been documented in 1915, 1948, and 2010–2011.
What is Tengger Caldera?
Tengger Caldera is a massive 16-km-wide volcanic complex in East Java, Indonesia, containing multiple nested calderas and post-caldera volcanic cones. The most famous feature is the inner Sandsea caldera (9 × 10 km), a flat expanse of volcanic sand called the 'Sea of Sand' from which several cones rise, including the active Bromo and the extinct Batok. The complex dates back approximately 820,000 years and includes five overlapping stratovolcanoes. Bromo, the youngest cone, has been the focus of nearly all historical eruptions. The entire complex lies within Bromo Tengger Semeru National Park.
Can you visit Mount Bromo?
Yes, Mount Bromo is one of Indonesia's most visited volcanoes and a major tourist destination. The classic experience involves watching sunrise from the Penanjakan viewpoint (2,770 m) on the caldera rim, then descending to cross the Sea of Sand and climbing 253 steps to Bromo's crater rim. The main access point is Cemoro Lawang, reached from Probolinggo (30 km) or Malang (50 km). The dry season (April–October) offers the best conditions. During volcanic eruptions, the approach to the crater may be closed while the wider caldera area remains accessible. National park entry fees apply.
What is the Kasada ceremony at Bromo?
The Kasada ceremony (Yadnya Kasada) is an annual Hindu ritual performed by the Tenggerese people at Bromo's active crater. Held on the 14th day of the Kasada month in the Tenggerese calendar (typically around June–July), participants climb to the crater rim and throw offerings of rice, vegetables, flowers, livestock, and money into the smoking vent to honor the gods and ensure agricultural prosperity. The ceremony draws thousands of participants and spectators. Some participants descend into the crater to catch offerings thrown by others — a practice that is both spiritually significant and physically hazardous given the volcanic gases and unstable terrain.
How big is Tengger Caldera?
The outer Tengger caldera is approximately 16 km wide, making it one of the larger calderas in Java. Within this, the inner Sandsea caldera (Lautan Pasir) measures 9 × 10 km and contains the post-caldera cones including Bromo and Batok. The caldera walls rise 200–600 m above the caldera floor, which sits at approximately 2,100 m elevation. The caldera rim reaches 2,329 m at its highest point. For comparison, this makes the Sandsea caldera roughly similar in size to Crater Lake in Oregon (8 × 10 km), though far more accessible.
Is Bromo dangerous?
Mount Bromo presents a moderate volcanic hazard. Its frequent eruptions are typically small (VEI 1–2), producing ash plumes and steam, but larger VEI 3 events have occurred (most recently in 2010–2011). The primary risks to visitors include volcanic gas emissions (SO₂) near the crater, ballistic projectiles during eruptions, and the unstable terrain of the crater rim. The larger risk is to surrounding communities from ashfall and lahars during the rainy season. Approximately 800,000 people live within 30 km. A repeat of the ~830 BCE VEI 4 caldera-related eruption, while unlikely, would be catastrophic.
What is the Sea of Sand at Bromo?
The Sea of Sand (Lautan Pasir) is a vast, flat expanse of grey volcanic sand and ash covering the floor of the Sandsea caldera within the Tengger complex. Measuring approximately 9 × 10 km, it creates a surreal desert-like landscape at 2,100 m elevation — an otherworldly environment in the middle of tropical, humid Java. The sand sea is composed of eroded volcanic deposits from the caldera walls and cones. Visitors cross it on foot, horseback, or by jeep to reach the base of Mount Bromo. The contrast between the barren sand sea and the surrounding tropical forests is one of Java's most striking natural spectacles.
When is the best time to visit Bromo?
The best time to visit Bromo is during the dry season, from April to October, when clear skies maximize the chance of witnessing the iconic sunrise over the caldera. June through August offers the driest and clearest conditions. The wet season (November–March) brings frequent fog, rain, and reduced visibility, though the landscape can be dramatic in misty conditions. The Kasada ceremony (usually June–July) offers a unique cultural experience but draws large crowds. Weekends and Indonesian holidays are extremely busy. Always check CVGHM volcanic alert levels before visiting, as crater access closes during eruptions.