Fossil finds
In which country is Koobi Fora ROck formation?
Kenya
What type of rock forms when sediment builds up in layers?
Sedimentary rock.
Is the environment around Lake Turkana today mostly dry or wet?
Mostly dry.
In undisturbed sedimentary rock layers, where are the oldest layers: at the top or at the bottom?
At the bottom.
What can extreme heat do to the results of radiometric dating?
It can make the results inaccurate by changing how elements behave in the rock.
What lake is next to Koobi Fora?
Lake Turkana
Name two examples of sediment mentioned in the article.
Soil and sand.
How was the region's earlier climate different from today's climate?
It was more humid and wet.
What law explains why older sedimentary rock layers lie below younger layers?
The law of superposition.
Give two reasons a fossil might be difficult to spot in rock.
It may be a similar color to the surrounding rock, and only a small part may be showing.
What does the article call our human ancestors?
Hominins.
What is the name of the rock made from volcanic material such as ash?
Tuff.
What process involving Earth's moving plates raised blocks of Koobi Fora?
Plate tectonics, or tectonic activity.
What happens to the unstable potassium isotope used to date tuff over time?
It decays into a stable isotope of argon.
Why does putting a fossil back together sometimes resemble solving a jigsaw puzzle?
Fragile fossils may break into small pieces that scientists must carefully fit together.
Scientists have found more than 10,000 fossils at Koobi Fora. What history do these fossils help them study?
The history of human evolution.
How can bones buried at the bottom of a lake or river become fossils in rock?
Sediment buries the bones. Over time, the sediment packs together into rock, and the bones can become fossils.
How did wind and water make fossils at Koobi Fora easier to find?
They wore away the raised rock and exposed fossils inside it.
How does comparing potassium and argon help scientists date a tuff layer?
Their relative amounts help scientists estimate when the tuff cooled and became solid rock.
Why do scientists give each fossil a special name or code?
To keep track of where fossils were found and the order in which scientists found them.
What do fossils from the Turkana Basin suggest about where humans originated and what happened later?
Humans originated in Africa and later migrated to other places
Explain how material from a volcano can become a layer of tuff at the bottom of a lake.
Ash and rock fall into the lake or travel there by air or rivers. The material settles and, over time, packs together into tuff.
Explain how tectonic activity and erosion worked together to expose fossils at Koobi Fora.
Tectonic activity raised blocks of rock. Wind and water then wore away the rock, making the buried fossils easier to see.
A fossil lies between an undisturbed 3-million-year-old layer below and a 2-million-year-old layer above. What is its likely age range? Explain.
Between 2 and 3 million years old. It is younger than the layer below it and older than the layer above it.
State the article's central idea and give two details that support it.
Fossils and rock layers help scientists understand human evolution and Earth's past. For example, potassium-argon dating estimates rock ages, and layer positions help scientists estimate fossil ages.