Stratovolcano (English spelling)

Japanese: 成層火山 - せいそうかざん（英語表記）stratovolcano

A volcano formed by alternating deposition of lava, pyroclastic material, or rock fragments. This is the most common form of volcano, and most of them have a steep cone shape. The slope is steepest near the summit, up to 35°, and the further away from the summit the slope becomes gentler, and the crater is small compared to the mountain body. It is composed of various volcanic rocks, from basalt to rhyolite, but andesite is the most common. Stratovolcanoes erupt thousands of times over their lifespan of millions of years. As relatively viscous thick lava solidifies and blocks vents, the pressure inside the volcano increases, causing repeated violent explosions and the release of large amounts of pyroclastic material such as volcanic ash. The alternating layers of ash and lava (strata) are not spread over the surface like a blanket, but are layered in a complex manner, forming earlobes or tongues. Volcanoes are the most numerous of all volcanoes, and in particular, Mount Mayon on the island of Luzon in the Philippines, Mount Momotombo towering northwest of Lake Managua in Nicaragua, and Mount Lengai (Ol Doinyo Lengai) in Tanzania, located south of Lake Natron, have steep cone-shaped formations formed by pyroclastic and lava flows. In Japan, there are Mount Fuji, Mount Yotei, Mount Iwaki, and Mount Kaimon.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

溶岩や火山砕屑物（火砕物），あるいは岩片が交互に堆積して生じた火山。最も一般的な火山の形態で，多くは急峻な円錐形をなす。山頂付近が最大35°と最も急で，山頂から遠ざかるほど斜面はゆるやかになり，山体に比して火口は小さい。玄武岩から流紋岩までさまざまな火山岩で構成されているが，一般に安山岩が多い。成層火山は数百万年の寿命の間に何千回も噴火する。比較的粘性の大きい厚い溶岩が固化して火道などをふさぐため，火山内部の圧力が強まり，激しい爆発を伴って火山灰など火砕物の大量噴出を引き起こすことを繰り返す。灰と溶岩の交互の層（地層）は毛布のように地表に敷きつめられた状態ではなく，耳たぶ状，舌状の形をなして複雑に重なっている。火山のなかで最も数が多く，特にフィリピンのルソン島にあるマヨン山，ニカラグアのマナグア湖北西にそびえるモモトンボ山，ナトロン湖南方にあるタンザニアのレンガイ山（オル・ドイニョ・レンガイ）などは，火砕流と溶岩流によってできた急峻な円錐形をなす。日本では富士山，羊蹄山，岩木山，開聞岳などがある。

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