Rarely a serious problem. Look-alikes: Jumping oak gall, tubakia leaf spot, oak leaf blister, other fungal leaf spots. Jumping oak gall Brown leaves appear on trees in the white oak group in late spring. Severe infections may cause the leaves to turn black, curl up and fall. On the underside are brown galls with the larva of a small wasp inside.
Volcanoes form when magma reaches the Earth's surface, causing eruptions of lava and ash. They occur at destructive (compressional) and constructive (tensional) plate boundaries. The immediate effects of volcanic eruptions can be devastating, but they may be beneficial in the long term.
Types of volcanoes. Volcanoes are divided into three main groups based on the shape of the volcano and the type of material they are made of: 1) shield volcanoes, 2) cinder cones, and 3) composite volcanoes. Shield volcanoes are formed when a large amount of free-flowing lava spills from a vent and spreads widely.olcanoes are divided into three main groups based on the shape of the volcano and the type of material they are made of: 1) shield volcanoes, 2) cinder cones, and 3) composite volcanoes. Shield volcanoes are formed when a large amount of free-flowing lava spills from a vent and spreads widely.