Self-study
Researchers working in Western Australia have discovered the oldest fragments of the Earth's early crust that have yet been identified: microdiamonds. █████ ███████████ ████████ ███████ ████ ██ ███████ ██████ ███ ████ ██████ ███ ███████ █████ ████ ████ █████████ █████ █████ ██ ███ ████ ██ ████ ███ ███ ███████ █████ ██ █████ █████ ████ ████ ██ ████ ███ ███████ █████ █████ ███ █████████ ██ ███ █████ ███████
Summary
Western Australian researchers have discovered microdiamonds, the oldest fragments of the Earth’s early crust yet identified. These microscopic crystals were formed 4.2 billion years ago, only 300 million years after the formation of the Earth itself. This discovery sheds light on how long it took for Earth’s crust to form.
Notable Valid Inferences
Earth’s crust did not take longer than 300 million years to begin to form.
19.
If the statements above are █████ █████ ███ ██ ███ █████████ ████ ████ ██ █████
a
The Earth's crust ████ ██ ██████ ████ ███ ███████ █████ ██ █████ ██ █████
Must be true. We know this because the microdiamonds that researchers found were part of the Earth’s early crust. If the microdiamonds existed 300 million years after Earth itself was formed, then Earth’s crust must have taken no longer than 300 million years to begin to form.
b
The Earth's crust █████ ██████ ██ ███ ████ ████ ██ ███ ███████ ██████████
Could be false. To claim this is where the Earth’s crust first formed is too extreme. We know that the microdiamonds the researchers found are the oldest fragments found to date. It is possible there exist older fragments that have not yet been found and that these fragments are not in what is now Western Australia.
c
The Earth's crust ████ ████████ ██ █████ ██ █████
Must be false. We know the microdiamonds the researchers found were part of Earth’s early crust, and these existed only 300 million years after the formation of Earth.
d
Microdiamonds were the █████ ██████████ ██ ███ ███████ █████ ██ █████
Could be false. To claim microdiamonds were the first components is too extreme. We know that they are the oldest fragments identified to date. It is possible that older fragments exist that have not yet been identified. These other fragments might be things other than microdiamonds.
e
All naturally occurring █████████████ ████ ██████ ██ ███ ████ ███ ███████ █████ ███ █████ ███████
Could be false. To claim all microdiamonds were formed at this time is too extreme. It is possible that there are other naturally occurring microdiamonds that formed after the ones the researchers identified.