Answer:
lighter than the solid rock around it, magma rises and collects in magma chambers. Eventually, some of the magma pushes through vents and fissures to the Earth's surface. Magma that has erupted is called lava. Some volcanic eruptions are explosive and others are not.
Positive feedback is a control system that sends a signal to ( increase) a response.
The lumbar nerves exit the intervertebral foramen under the pedicle of the same numbered vertebral body.
lumbar sacral: intervertebral
coccygeal: vertebral