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.
The vast majority of volcanic activity occurs where tectonic plates collide, called convergent boundaries, or spread, called divergent boundaries. However, there is a special class of volcanoes that form within plates. These inter-plate volcanoes are known as hotspot volcanoes.Hotspot volcanoes that form under continental plates are called super volcanoes, representing the most powerful and violent volcanoes on Earth.owever, there is a special class of volcanoes that form within plates. These inter-plate volcanoes are known as hotspot volcanoes. Hotspot volcanoes that form under continental plates are called super volcanoes, representing the most powerful and violent volcanoes on Earth.