Observer Online

The landforms of central New Mexico and the rock they are made of.

An adult geologist with a hand lens crouched at a rock outcrop, notebook on the ground 01

The Rift [01]

Albuquerque Basin

The basin is one of a chain along a continental rift: the crust here is pulling apart, which puts it in the same category of landform as East Africa rather than an ordinary river valley.

Read the entry
Most of what is known about the fill under the valley was established at outcrops like this.Plate 01

Where the break shows

All twenty-one entries
Sunset light glows orange on a granite cliff above a pine forest valley

Sandia Mountains

A tilted fault block with a granite core and a limestone cap, whose west face is essentially the exposed side of the break.

Fault Blocks
Layered mountain ridges fade into haze beyond a forested, grassy hillside

Jemez Mountains

A volcanic field sitting on the rift's western margin, built and rebuilt over more than ten million years.

Volcanic Fields
Boulders etched with ancient petroglyphs scattered across a rocky desert canyon floor

Petroglyph National Monument

Tens of thousands of images pecked into the desert varnish on basalt along the escarpment west of the river.

Basalt and Record

The register

Eight of the ten mapped landforms

The full register
  1. Layered mountain ridges fade into haze beyond a forested, grassy hillside 01 Jemez Mountains 35.900 N  106.533 W
  2. Sheer tuff cliffs rise above a dense pine forest in a canyon landscape 03 Bandelier Tuff 35.779 N  106.321 W
  3. Cone-shaped tent rock formations rise steeply along a narrow canyon trail with hikers below 04 Kasha-Katuwe Tent Rocks 35.660 N  106.408 W
  4. Sunset light glows orange on a granite cliff above a pine forest valley 05 Sandia Mountains 35.209 N  106.447 W
  5. Forested ridgeline of the Manzano Mountains under a dramatic cloudy sky with sunbeams 06 Manzano Range 34.790 N  106.400 W
  6. A lone figure walks across a vast desert plain beneath a jagged peak 07 Ladron Peak 34.435 N  107.085 W
  7. Boulders etched with ancient petroglyphs scattered across a rocky desert canyon floor 08 Petroglyph National Monument 35.136 N  106.762 W
  8. Cracked salt flat stretches toward distant mountain ranges under a pale sky 10 Socorro magma body 34.051 N  106.888 W

Where the dating is contested

Two eruptions, several ages

Two eruptions from the Jemez field laid down the Bandelier Tuff. Published ages for both still differ by more than a hundred thousand years depending on the method.

Otowi Member · earlier work~1.4 Ma
Otowi Member · argon–argon~1.61 Ma
Tshirege Member · earlier work~1.1 Ma
Tshirege Member · argon–argon~1.25 Ma

Bandelier Tuff

A long basalt escarpment above the valley floor in low winter sun
Something like twenty-four thousand images are pecked through the varnish on the basalt west of the river. Basalt and Record

Ten mapped points

Coordinates in full

Every landform on the site has a position. Ten of them are plotted here; each name opens its entry.

02 Jemez Mountains01 Valles Caldera03 Bandelier04 Tent Rocks05 Sandia Mountains08 Petroglyph09 Albuquerque06 Manzano Mountains07 Ladron Peak10 Socorro NEW MEXICO Landform in the register 100 km N
From Jemez Mountains at 36.01° N to Socorro at 34.05° N: 220 km end to end. The four northern points all belong to the Jemez volcanic field or to the ash it laid down.

It has not stopped

Ground in Motion
Cracked salt flat stretches toward distant mountain ranges under a pale sky

Socorro magma body

A large sheet of magma sits in the crust beneath Socorro, and the ground above it is measurably rising.

Ground in Motion
A satellite dish antenna on a ladder tower rises from a concrete pedestal in the desert

Geodesy

Continuous satellite positioning measures motion of a few millimetres a year, which is how the rate is actually known.

Ground in Motion