Santa Fe

Key facts

Country

United States

Diameter

9 km

Age

probably between about 350 million and 1.2 billion years

Location

35.75° N, 105.93° W

The Santa Fe impact structure lies in the Sangre de Cristo Mountains just north-east of Santa Fe, the capital of New Mexico, in the United States. Nothing remains of the crater's shape: the structure is known only from the shattered rocks along a mountain road.

Discovery. In 2005 a geologist driving along the road from Santa Fe to Hyde Memorial State Park noticed that rocks in a road cut, made decades earlier, were covered in shatter cones, cone-shaped fractures with branching grooves that form only under the shock of an impact. Thousands of drivers had passed them every year without realising what they were. Microscopic study later found shocked quartz, confirming an impact.

What it hit. The impactor struck ancient Precambrian crystalline rocks, granites and metamorphic rocks more than 1.4 billion years old, which form the core of the mountains. The shatter cones occur over a stretch of about 1.6 km along the road and are thought to mark part of the central area of the original crater.

Size and age. Erosion has removed the crater, so its original size is uncertain; estimates range from about 6 to 13 km. The age is also poorly known. The impact must be younger than the ancient rocks it shocked and older than the undisturbed Carboniferous limestones, about 350 million years old, that lie on top of them nearby; within that long window, estimates vary.

Why it matters. Santa Fe shows that impact structures can hide in plain sight, even beside a busy road near a state capital. The impactor is unknown.

Visiting. The shatter cones can be seen from the roadside. Park safely, take care of traffic, and do not hammer the outcrops.

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