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.
When magma reaches the surface, it is called lava. When lava has cooled, it forms a type of rock called igneous rock, which means âfrom fireâ. Volcanoes can form in 3 major ways: 1. Volcanoes at Convergent Boundaries Most volcanoes form at convergent boundaries called subduction zones. At these boundaries, oceanic plates subduct below continental plates. As the denser oceanic plate sinks down, heat from the Earth melts the plate and the rock becomes magma.