The timeline marks three events from Earth's early history. Which interval of geologic time includes all three?

A timeline blank begins with the Cambrian explosion and ends with the end-Permian mass extinction. Which era does the blank represent?

A timeline blank covers about 4.6 to 4.0 billion years ago, before the Archean begins. Which eon belongs in the blank?

The timeline marks fossil stromatolites at about 3.5 billion years ago, between two eon boundaries. Which eon contains that point?

A timeline point at about 2.4 billion years ago marks the Great Oxidation Event, between two eon boundaries. Which eon contains that point?

The timeline shows the Ediacaran Period, from about 635 to 539 million years ago, which includes the Ediacaran biota and ends just before the Cambrian explosion. Which eon is it in?

A timeline point at the start of the Cambrian shows a rapid increase in animals with hard shells and skeletons. Which era begins there?

A timeline point in the Devonian marks the first forests and early tetrapods moving onto land. Which era contains those events?

A timeline point in the Pennsylvanian marks coal-forming swamp forests and the first reptiles. Which era contains that point?

A timeline point at about 252 million years ago marks the largest mass extinction and the close of an era. Which era ended there?

A marine arthropod with a hard, segmented exoskeleton and compound eyes became abundant in Cambrian seas and died out at the end of the Permian. Which fossil group is described?

Dark, pencil-like colonial fossils in Ordovician and Silurian shales are used to correlate early Paleozoic strata. Which group is described?

Two-valved “lamp shells” dominated many Paleozoic seafloors and are common in marine limestone and shale. Which fossil group is described?

Mississippian limestones are so rich in stalked sea-lily remains that the interval is called the “Age of” which fossil group?

Large aquatic arthropod predators, often called sea scorpions, were most diverse in Silurian and Devonian rocks. Which group is described?

Armored jawed fish such as Dunkleosteus were prominent during the Devonian “Age of Fishes.” Which fossil group is described?

Tiny rice-grain-shaped foraminifera are common in Pennsylvanian and Permian limestones and disappeared at the end-Permian extinction. Which group is described?

Colonial “moss animals” that first appear in Ordovician marine rocks built branching or lacy fossils. Which group is described?

Tiny toothlike phosphatic elements from extinct eel-like animals are important Paleozoic microfossils for dating marine rocks. Which group is described?

A 300-million-year-old paleogeographic map shows one C-shaped continent made from nearly all major landmasses. What is that supercontinent called?

A Permian map shows Pangaea surrounded on most sides by one enormous global ocean. What is the surrounding ocean called?

A Permian map shows the open side of C-shaped Pangaea facing east and enclosing a smaller ocean. What ocean occupied that open side?

A Late Ordovician map places a large southern continent over the South Pole with continental ice sheets. Which landmass is shown?

An early Paleozoic map shows Laurentia and Baltica separated by a wide ocean that later closed during Appalachian mountain building. Which ocean was between them?

A late Paleozoic map shows Gondwana colliding with Laurussia along the future eastern edge of North America. What mountain belt did this collision help build?

A Mississippian map shows a broad shallow sea covering much of central North America. What rock type would most likely form there?

Banded iron formations alternate iron oxide with chert and are common in rocks older than about 2 billion years. What Earth-system change do they record?

A Proterozoic rock unit contains red beds stained by hematite on land. What change in Earth systems does that rock best record?

A late Proterozoic diamictite contains unsorted clasts, scratched stones, and dropstones in fine sediment. What environment does it record?

A Precambrian limestone has layered dome-shaped stromatolites. What do those structures record?

A rock near the Precambrian-Cambrian boundary preserves quilted impressions of soft animals but almost no shells. What does that fossil record show?

A Mississippian limestone is packed with broken crinoid stems. What environment does the rock most likely record?

A Pennsylvanian rock layer is coal with fern and lycophyte fossils. What ancient environment produced it?

A Cambrian sandstone contains many vertical burrows cutting across bedding. What change in life does this rock record?

Four events are Cambrian explosion, end-Ordovician extinction, Devonian first forests, and end-Permian extinction. What order is oldest to youngest?

Four Paleozoic changes are first land plants, first jawed fish, first forests, and first reptiles. What order is oldest to youngest?

Four late Paleozoic events are Mississippian crinoid seas, Pennsylvanian coal swamps, Permian Pangaea, and end-Permian extinction. What order is oldest to youngest?

Four Paleozoic events are early shelled animals, primitive fish, first amphibians, and coal-forming swamps. What order is oldest to youngest?

Four events are Gondwana glaciation, Silurian jawed fish, Devonian mass extinction, and end-Permian mass extinction. What order is oldest to youngest?

Four tectonic events are Iapetus separates continents, Iapetus closes, Gondwana collides with Laurussia, and end-Permian extinction. What order is oldest to youngest?