Scoria (English spelling)

Japanese: スコリア（英語表記）scoria

Pyroclastic material ejected by volcanic eruptions that has a porous internal structure and is black or dark brown in color. It is also called scoria. There is no definition of size, but it generally refers to volcanic lapilli with a diameter of 2 to 64 mm and volcanic rock blocks with a diameter of 64 mm or more. Also, the same porous material that is white or light gray in color is called pumice (floating stone). Scoria is mainly produced from basaltic magma that contains a lot of mafic minerals (magnesium, iron). When the magma (lava) cools and becomes viscous, the dissolved volatile components (mainly water) vaporize all at once, turning it into coke-like rock fragments with many bubbles. The bubbles are large and come in various shapes. When scoria falls unsolidified, it sticks to itself and becomes welded scoria. Also, because of its low apparent density, it is blown far away like pumice and volcanic ash, but the amount of scoria ejected is small. When volcanic gases and ash mix with scoria and it flows down the slopes of a volcano at high speeds (→ pyroclastic flows), it is called a scoria flow. Scoria cones are cones that are mainly composed of scoria and are formed in the cones around the crater.

Scoria
scholia

Annotations written in the margins of classical manuscripts by ancient philologists. Many of them date back to the Alexandrian period, and they provide insight into the textual criticism and etymological research of that period. (→ Alexandrian School)

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

Japanese:

火山の噴火で放出された火山砕屑物のうち，多孔質の内部構造をもつ黒色，暗褐色のもの。岩滓（がんさい）ともいう。大きさの定義はないが，直径 2～64mmの火山礫，直径 64mm以上の火山岩塊をおおむねさす。また，同じ多孔質であるが色が白色，淡灰色のものを軽石（浮石）という。スコリアはおもに苦鉄質鉱物（マグネシウム，鉄）を多く含む玄武岩質のマグマから生じる。冷やされて粘性が高まったマグマ（溶岩）から，溶け込んでいた揮発性成分（おもに水）が一気に気化することで，多数の気泡をもつコークス状の岩片となる。気泡は大きく，その形はさまざまである。スコリアは未固結のまま落下すると互いに粘着し合って溶結スコリアとなる。また，見かけの比重が小さいことから，軽石や火山灰と同様に遠方に飛ばされるが，噴出量は少ない。高温の火山ガスや火山灰などと混じって，火山斜面を高速で流下することもあり（→火砕流），スコリア流（岩滓流）と呼ばれる。また，火口の周囲に堆積する円錐形の砕屑丘のうち，スコリアを主体とするものをスコリア丘（岩滓丘）という。