Pembahasan OSNP Kebumian 2025 No 1-4

Summary

This video is the first in a series discussing the 2025 OSNP Earth Science exam, focusing on questions 1–4 related to geology. It reviews the volcanic activity of Mount Lewotobi in East Flores, detailing its stratovolcano structure, explosive eruptions, and historical activity. The video explains plate tectonics behind its formation, distinguishing between oceanic and continental plates, and introduces volcanic morphologies, magma compositions, and eruption products. Key concepts such as stratovolcano layering, intermediate magma from partial melting, and pumice formation are clearly illustrated. This engaging tutorial helps students understand essential Earth Science principles while providing step-by-step problem-solving strategies for the exam.

Takeaways

• 🌋 The video discusses OSNP Kebumian 2025 questions 1–4, focusing on Gunung Lewotobi in Flores Timur, NTT.
• 🗻 Gunung Lewotobi consists of two peaks: Lewotobi Male (active) and Lewotobi Female (alert but stable).
• ⚡ The July 2025 eruption of Lewotobi Male produced an 18 km high ash column, impacting local airports and agriculture.
• 🌐 Gunung Lewotobi formed due to subduction of the Indo-Australian oceanic plate beneath the Eurasian continental plate (correct mechanism: subduction, not collision).
• 🧩 Subduction typically involves the denser oceanic plate descending beneath the lighter continental plate; the reverse scenario is rare and called obduction.
• 🏔️ Lewotobi Male is classified as a stratovolcano, characterized by alternating layers of lava flows and solid eruption materials.
• 🔥 Stratovolcano eruptions are both explosive and effusive, creating layered volcanic structures over time.
• 🌋 Lava from stratovolcanoes generally has an intermediate composition, formed from partial melting of the subducting oceanic plate.
• 🪨 Volcanic eruption products vary in density and texture; pumice is the lightest with many vesicles, while scoria is heavier and basaltic, and obsidian forms from rapid cooling of acidic magma.
• 📚 Understanding volcano types, eruption styles, lava composition, and eruption products is crucial for studying earth sciences and volcanic hazards.

Q & A

What type of volcanic system does Gunung Lewotobi form, and what are its two peaks called?

Gunung Lewotobi forms a complex stratovolcanic system with two peaks called Lewotobi Laki-laki (male) and Lewotobi Perempuan (female).

What major volcanic activity occurred at Lewotobi Laki-laki in July 2025?

Lewotobi Laki-laki experienced an explosive eruption with an ash column reaching about 18 km, affecting nearby agriculture and the northern airport.

How is the formation of Gunung Lewotobi explained in terms of plate tectonics?

Gunung Lewotobi formed due to the subduction of the Indo-Australian oceanic plate beneath the Eurasian continental plate. Subduction involves the denser oceanic plate sinking below the lighter continental plate.

Which answer choice correctly describes the plate interaction forming Gunung Lewotobi?

Answer E: Gunung Lewotobi was formed by the subduction of the Indo-Australian oceanic plate beneath the Eurasian continental plate.

What are the main types of volcano morphology discussed, and which type does Lewotobi Laki-laki belong to?

The main types are shield volcanoes, stratovolcanoes, and caldera volcanoes (Gunung Marwah). Lewotobi Laki-laki is a stratovolcano, characterized by alternating layers of lava and pyroclastic material.

What type of volcanic eruptions build stratovolcanoes, and what material accumulates during these eruptions?

Stratovolcanoes are built by alternating explosive and effusive eruptions, which deposit layers of lava and solid pyroclastic material.

What is the typical magma composition of a stratovolcano like Lewotobi?

The magma is intermediate in composition, formed through partial melting of subducted oceanic plates, making it more viscous and silica-rich than basaltic magma.

Which volcanic rock is the lightest and most vesicular, often produced in explosive eruptions?

Pumice is the lightest and most vesicular volcanic rock, formed from explosive eruptions of silica-rich magma.

How does a shield volcano differ from a stratovolcano in terms of lava flow and shape?

A shield volcano has very fluid lava, creating a broad and gently sloping shape, whereas a stratovolcano has alternating layers of viscous lava and pyroclastic material, forming steep, layered slopes.

What is the significance of the partial melting process in subduction zones for volcanic activity?

Partial melting in subduction zones transforms oceanic basalt into intermediate magma, which is more viscous and silica-rich, leading to explosive eruptions and the formation of stratovolcanoes.