Volcanoes – Grade 10 Lecture Review

These flashcards review key points from the Grade 10 lecture on plate tectonics, types of volcanoes, Philippine active volcanoes, and disaster preparedness.

What key idea does the theory of plate tectonics explain?

How major landforms such as mountains, volcanoes, and earthquake zones are created by movements of Earth’s lithospheric plates.

In which decade was the theory of plate tectonics solidified in the earth-science community?

The 1960s.

Name the seven major lithospheric plates identified by the World Atlas.

African, Antarctic, Eurasian, Indo-Australian, North American, Pacific, and South American plates.

Define a volcano.

An opening in a planet’s or moon’s crust through which molten rock, hot gases, and other materials erupt, often forming a hill or mountain of layered rock and ash.

Into what three activity categories are volcanoes classified?

Active, dormant, and extinct.

Which type of plate boundary produces volcanic activity when plates rip apart?

A divergent plate boundary.

At what type of plate boundary does subduction create a line of volcanoes on the overriding plate?

A convergent plate boundary.

Give three examples of active volcanoes in the Philippines.

Possible answers include Mt. Mayon, Mt. Taal, Mt. Kanlaon, Mt. Iraya, and Mt. Smith.

According to Table 1, which Philippine volcano has the greatest number of historical eruptions?

Mt. Mayon, with 52 recorded eruptions.

Which volcano in Table 1 last erupted in 1454 yet is still classified as active?

Mt. Iraya.

How can scientists determine that a volcano is active?

By evidence of historic eruptions, current seismic or fumarolic activity, and monitoring data indicating magma movement.

What are composite (strato-) volcanoes composed of?

Alternating layers of lava flows and rock fragments (ash, cinders).

List two characteristic features of composite volcanoes.

They often form large, steep, snow-capped peaks, commonly exceed 2 500 m in height, and can reach ~400 km³ in volume.

Why do shield volcanoes have broad, gentle slopes?

They are built by very fluid, basaltic lava that spreads widely instead of piling into steep cones.

Where do shield volcanoes commonly form?

Over hot spots away from plate boundaries, along mid-ocean ridges, and in some subduction-related volcanic arcs.

What is typical of shield-volcano eruptions?

Low-explosivity lava fountaining that forms cinder and spatter cones near the vent.

Name two famous shield volcanoes in Hawaii.

Mauna Loa and Kilauea.

What type of eruption usually builds cinder cones?

Strombolian eruptions.

Describe the typical size of a cinder cone.

Rarely more than 250 m high and 500 m in diameter.

What are volcanic cinders?

Lava fragments that solidify in the air and fall back around the vent, building the cone.

Give a classic example of a cinder cone and a notable fact about its growth.

Paricutín in Mexico, which rose about 300 ft (≈90 m) in only five days after its birth in 1943.

Are volcanoes randomly distributed across Earth’s surface?

No. They occur mainly along plate boundaries and the edges of continents, often where earthquakes also happen.

Why is disaster preparedness important for communities near active volcanoes like Taal?

Advance planning (evacuation routes, emergency kits, masks, and monitoring alerts) can save lives and property when an eruption occurs.