Structures known as "coulees" are formed when "domes" of this substance spread out slightly.
This substance's aspect ratios and effusion rates were studied by George P. L. Walker to determine its emplacement mechanisms. The "ponding" of this material can create cross-cutting patterns known as "hackly jointing". A kipuka is completely surrounded by this material, a rare form of which contains sodium and carbonates and is formed at Ol Doinyo Lengai in Tanzania. The debris on top of this material adopts mostly polygonal shapes in an intermediate or "andesitic" form of this material that is known as its (*) "block" variety. Structures known as "coulees" are formed when "domes" of this substance spread out slightly. This substance, which forms into characteristically pillow-shaped structures underwater, comes in high- and low-viscosity examples called aa (ah-ah) and pahoehoe (puh-HOY-hoy). For 10 points, name this molten rock that flows on Earth's surface, unlike magma.
This substance's aspect ratios and effusion rates were studied by George P. L. Walker to determine its emplacement mechanisms.
lavas [accept lava flows or block lava or lava domes or rhyolitic lavas or intermediate lavas or andesitic lavas; accept magmas before “ponding”; do not accept or prompt on “magma” after “ponding”] &lt;Hart&gt;