When seedless plants died became buried deep in the earth, and were exposed to heat and pressure, coal formed. Learn more about how coal seams in the Powder River Basin of Wyoming may have originated from raised bogs.
BasicStudents matched to this level have a partial mastery of prerequisite knowledge and skills fundamental for proficient work.
At Grade (Proficient)Students matched to this level have demonstrated competency over challenging subject matter, including subject matter knowledge, application of such knowledge to real-world situations, and analytical skills appropriate to subject matter.
AdvancedStudents matched to this level are ready for material that requires superior performance and mastery.