Scientists divide earth into three main layers: the core, the mantle, and the crust. how are these three layers identified?

by their chemical composition

by their structural features

by their plate tectonics

by their physical properties

2. sketch the inside of the bean nodule, and describe or label what you observed with the hand lens.

1. seamount a raised footwall block between normal fault creates this 2. syncline break between rocks where a hanging wall rises relative to a footwall 3. hot spring on rolling hills, this a dip between hills 4. volcanic neck created when a block with hanging walls slips down between normal faults 5. caldera underwater volcano that never reaches above sea level 6. horst natural hot water on earth's surface containing many minerals 7. graben underwater volcano whose top is eroded flat by waves 8. crater less than a mile in diameter; looks like a bowl at the top of a volcano 9. guyot magma that filled the central vent that remains after the volcano has eroded 10. reverse fault over 1 mile in diameter; looks like a bowl over a volcano

Why are current extinctions of concern to enviromentalists?