UNEARTHING MINDANAO ISLAND; A COMPREHENSIVE SYNTHESIS OF ITS

TECTONIC ACTIVITY AND IMPLICATION

The second largest island in the Philippines is Mindanao. Mindanao is a geologically diversified
territory with rich mineral resources, a complex tectonic history, and a variety of landforms
(Robert L. Pendleton Geographical Review 32 (2), 180-210, 1942. (Luisa G. Tejada et al. 2009)
state that the island is located in the Philippine Mobile Belt, a tectonic plate boundary zone where
the Philippine Sea Plate subducts beneath the Eurasian Plate. Because of its unique geological
environment, Mindanao features a dynamic landscape that is characterized by numerous fault
systems, mountains, and volcanoes.

Mindanao Island is situated inside the pacific Ring of fire, an area well-known for its tremendous
tectonic activity and volcanic eruption, it is home to a number of active volcanoes , (RD
Jacobson – 2012). A prominent feature of Mindanao is the Philippine Fault Zone, is located in a
seismically active region and is traversed by several major fault line, including the Cotabato
Trench, the Davao Trench, the Surigao Trench, and the Sulu Trench (Ramon D Quebral et
al.,1996) which are known to cause earthquakes a major strike-slip fault that runs across the
island. This fault system plays a crucial role in the tectonic evolution of the region,
accommodating the lateral motion between the Philippine Sea Plate and the Eurasian Plate. The
movement along this fault has led to seismic activity, and the island is vulnerable to earthquakes.
The fault lines, where the Earth's plates are moving, are earthquake generators. On December 2,
2023, at 22:37 PST (14:37 UTC), a magnitude 7.6 earthquake occurred of the island of Mindanao.
The Philippine trench which runs east of the Philippines islands represents a major subduction
zone where the Philippine Sea Plate subducts westwards. At its southern portion, it runs north-
south from the eastern coast of Mindanao to the northern part of Halmahera Island. According to
PHIVOLCS 1,583 aftershocks recorded within four days of the earthquake, 192 aftershocks above
M 4.5 were recorded by the USGS; the aftershock sequence occurred southeast of the mainshock.
The largest aftershock, measuring 6.9 struck on December 4, 2023 occurring north of the
aftershock sequence near Cagwait. However, PHIVOLCS said that it was a separate earthquake.
The December 2, 2023 earthquake was described as the first major earthquake in the area since a
doublet 7.1 and 7.5 earthquake.

In addition, Davao de Oro in Eastern Mindanao is one of the seismically active regions in the
country because of the presence of active faults that include the East Compostela Valley, West
Compostela Valley, Central Compostela Valley, Nabunturan, Caraga River, and Mati Segments of
the Philippine Fault (Perez et al., 2015), There are other nearby local faults, some of which may
be covered by recent deposits, that could be source of minor to strong magnitude earthquake. The
highest magnitude recorded in the Davao de Oro earthquake series is Mw 5.9. This magnitude
was felt at a very strong intensity level in the municipalities of Maco, New Bataan, Maragusan,
Mawab and Nabunturan.

Furthermore the Philippine Fault system is a major fault system that runs through the Philippines.
It extends from Luzon in the north to Mindanao in the south. The Mindanao segment of the
Philippine Fault system is known as the Mindanao Fault. According to a geologist, Jeffrey Perez,
that the Philippine Fault, which begins in the Ilocos Region and extends for around 1,200
kilometers, includes the segments’ fault in Davao de Oro and he also said, that the lengthier the
fault, the greater the magnitude it can produce. Thus, no wonder that many areas in Mindanao
experience damaging earthquakes.
One of the tectonic activity happened here in Mindanao is a Volcanic eruptions. A number of
active volcano including Mt. Apo in Davao City, Mt. Matutum in South Cotabato, and Mt. Parker
are also found in Mindanao Island, each peak have a different geological features and historical
significance. The presence of these volcano is a result of the subduction of the Philippine Sea
Plate beneath the Sunda Plate, creating magma chambers and volcanic eruptions, because
subduction occurs when one tectonic plate is forced beneath another plate, creating a subduction
zone. In the case of Mindanao, the Philippine Sea Plate is subducting beneath the Sunda Plate. As
the Philippine Sea Plate sinks deeper into the Earth's mantle, it generates intense heat and
pressure. This process leads to the melting of rocks and the formation of magma chambers
beneath the Earth's surface. Geosciences, 2022.

In conclusion, Mindanao Island in the Philippines exhibits significant tectonic activity due to its
location in a seismically active region. The convergence of tectonic plates, including the
Philippine Sea Plate and the Sunda Plate, has resulted in the formation of numerous active
volcanoes, such as Mount Apo, Mount Matutum, and Mount Parker. These volcanoes are a
testament to the intense geological forces at play in the region. The island's position within the
Philippine Mobile Belt exposes it to seismic hazards, while its mountains, volcanoes, and mineral-
rich soils contribute to its geological complexity. As Mindanao continues to undergo geological
processes, understanding its dynamic landscape is crucial for both hazard mitigation and
sustainable development in this vibrant and geologically active part of the Philippines.
Additionally, Mindanao experiences frequent earthquakes, often triggered by the movement and
interaction of these tectonic plates. The tectonic activity in Mindanao has both positive and
negative implications. On the positive implication, it contributes to the island's natural resources,
such as fertile volcanic soil and geothermal energy potential. The volcanic activity also shapes the
landscape, creating unique features and supporting diverse ecosystems on earth. On the other
hand, the region is prone to volcanic eruptions and earthquakes, which can pose risks to the
people, local communities and infrastructure. It is crucial to monitor and study the tectonic
activity in Mindanao Island to enhance preparedness, mitigate risks, and ensure the safety of the
island's inhabitants and give awareness to the people of what should the first thing they do during
of an unpredictable phenomenon such as an earthquake.
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