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.
Volcanoes can form in three geologic settings, all of which result in the melting of rock in the upper part of the mantle. The rock in the mantle is very hot but is kept solid under immense pressure. Some volcanoes form at divergent boundaries where two of Earth's tectonic plates pull apart. The crust is thin at these boundaries, reducing pressure on the mantle, allowing some melting to occur, forming molten rock called magma. This rises to the surface, forming volcanoes.