In a thread which was shut down by moderators, the subject of the Chicxulub crater was raised with the tired old creationist argument one needed a time machine to prove such a crater existed and caused by an asteroid impact.
The oldest impact structure found on Earth is the Yarrabubba impact structure in Western Australia which makes Chicxulub a baby by comparison and has been dated to 2.229 billion years old compared to Chicxulub 66 million years old.
The original crater of the impact structure has long since eroded leaving no visible structure so how do scientists know the crater once existed and was caused by an impact event without having the luxury of a time machine.
Here are some examples.
Shocked quartz.
When subjected to impact events quartz is altered by heat and pressure.
Quartz undergoes a sudden compression and the attendant rise in temperature produces effects not normally observed in quartz.
Shocked quartz has a different microscopic structure to normal quartz.
Under intense pressure, the crystalline structure of shocked quartz is deformed along planes inside the crystal and shows up as lines under a microscope which are called planar deformation features (PDFs) or shock lamellae.
Impactites.
These are terrestrial rocks which has been melted or altered by the heat and pressure of the impact event.
Shatter cones.
These are terrestrial rocks affected by the shock wave of the impact.
The shock waves cause the rocks to fracture into a distinctive cone shape known as a shatter cone.
Magnetic anomalies.
Impacts can cause magnetic anomalies where heat can destroy rock magnetization, displace magnetized rocks from the impact area and form new magnetic phases in the rock.
Such anomalies are detected using magnetometers.
Gravity anomalies.
Large impact structures leave distortions on the surface where there is less mass in the distortion.
This affects the Earth’s gravitational field, which can be detected using instruments such as gravimeters, gravity gradiometers and radar altimeters.
The peer reviewed paper for the Yarrabubba impact structure.
The oldest impact structure found on Earth is the Yarrabubba impact structure in Western Australia which makes Chicxulub a baby by comparison and has been dated to 2.229 billion years old compared to Chicxulub 66 million years old.
The original crater of the impact structure has long since eroded leaving no visible structure so how do scientists know the crater once existed and was caused by an impact event without having the luxury of a time machine.
Here are some examples.
Shocked quartz.
When subjected to impact events quartz is altered by heat and pressure.
Quartz undergoes a sudden compression and the attendant rise in temperature produces effects not normally observed in quartz.
Shocked quartz has a different microscopic structure to normal quartz.
Under intense pressure, the crystalline structure of shocked quartz is deformed along planes inside the crystal and shows up as lines under a microscope which are called planar deformation features (PDFs) or shock lamellae.
Impactites.
These are terrestrial rocks which has been melted or altered by the heat and pressure of the impact event.
Shatter cones.
These are terrestrial rocks affected by the shock wave of the impact.
The shock waves cause the rocks to fracture into a distinctive cone shape known as a shatter cone.
Magnetic anomalies.
Impacts can cause magnetic anomalies where heat can destroy rock magnetization, displace magnetized rocks from the impact area and form new magnetic phases in the rock.
Such anomalies are detected using magnetometers.
Gravity anomalies.
Large impact structures leave distortions on the surface where there is less mass in the distortion.
This affects the Earth’s gravitational field, which can be detected using instruments such as gravimeters, gravity gradiometers and radar altimeters.
The peer reviewed paper for the Yarrabubba impact structure.
Precise radiometric age establishes Yarrabubba, Western Australia, as Earth’s oldest recognised meteorite impact structure - Nature Communications
The ~70 km-diameter Yarrabubba impact structure in Western Australia has previously been regarded as among Earth’s oldest meteorite craters, but has hitherto lacked absolute age constraints. Here, the authors determine a precise impact age of 2229 ± 5 Ma, which extends the terrestrial cratering...
www.nature.com
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