Lava flows are the least hazardous of all processes in volcanic eruptions. How far a lava flow travels depends on the flows temperature, silica content, extrusion rate, and slope of the land. A cold lava flow will not travel far and neither will one that has a high silica content. Such a flow would have a high viscosity<span> (a high resistance to flow). A basalt flow like those in Hawai'i have low silica contents and low viscosities so they can flow long distances. Such a flow can move as far away as 4 km from its source and have a thickness of 10 m (Bryant, 1991). These flows can move at rates of several kilometers per hour (Scott, 1989). </span><span>More silica-rich flows can move as far away as 1.3 km from their sources and have thicknesses of 100 m (Bryant, 1991). These flows can move at rates of a few to hundreds of meters per hour (Scott, 1989). If a lava flow is channelized or travels underground in a lava tube then the distance it travels is greatly extended.</span>
It is called seismic waves. That should help:)
Answer : scientists determine the absolute age of a rock in millions of years before present rather than just the age of the rock relative to the rock units around it. This information helps geologists develop more precise geological history models for the rocks and regions they study.
Explanation:
The Sahel is located in Africa. It is the region in Africa that transitions from the Sahara to the Sudanian Savanna. It stretches across in the region from the West of Africa to the East and includes parts of Senegal, Mauritania, Mali, Burkina Faso, Algeria, Niger, Nigeria, Chad, Sudan, South Sudan, Eritrea, CAR, Cameroon, and Ethiopia.
