Geology of National Parks:

Rio Grande Rift

1) Rio Grande Rift

2) Other rift systems

3) Connection to Europe

Rio Grande River

Basin

• Headwaters in CO,

outlet in Gulf of Mex.

• 1,896 mi. long

• 182,200 sq. mi. OR

336,000 with

“endorheic” (closed)

basins

• 80% drained for ag

and urban uses

• **Formed within rift

valley

Rio Grande Gorge

(near Taos)

WESTERN UNITED STATES

RGR currently 450 mi. long from Leadville, CO to near

Mex. Border at Ciudad Juarez, Mex., across from El

Paso

RGR – Note the broad valley bordered by

mountains to E and W, and the volcanics

DVD

New Mexico Natural

History Museum

“Each year across the rift

spreads the equivalent of

about one-twentieth of an

inch, or 1.0 – 2.5

millimeters, over a length

of about 600 miles. The

rate is lower than

expected.” CU Researcher

From Campbell Science

625 mi.

From National Park Service

From: National Science Foundation

RGR Formation phases:

1. Early - Began in

southern portion

between 35-29 MYA

2. Second phase about

15 MYA opened

central and northern

part and igneous

intrusions

3. Spreading

continues, and land

on both the eastern

and western side of

this rift continues to

rise

4. Modern volcanism

150 – 2 KYA

Likely process initiating

continental expansion -

The rift is formed where a

section of the Earth’s crust

arched, weakened, and

spread apart due to heat

from basaltic magma

welling up from the mantle

35-29 MYA.

New Mexico Natural

History Museum

Crust Thickness:

• 28 mi

• 22 mi

• 31 mi

From:

http://www.geo.utep.edu/pub/hector/

Regional_Research/

RGR geologic section goes from Precambrian to recent

sand and gravel deposited from surrounding erosion and

fill that continues today as mountains continue to rise

~25,000’

From: Emporia State Univ.

Graphics from Univ. of Sydney and Wiki

Graphics from

Univ. of

Sydney and

Wiki

Listric faults

Plate and Rift

System: Other

Rift Zones

East Africa

Rift Zone

(Afar

region)

European Cenozoic Rift System

(Eurasian and African Plates)

Baikal Rift Zone

(Eurasian and Amurian

Plates)

and Lake Baikal

Lake Baikal:

• Largest freshwater lake by vol.

• 20% of world’s unfrozen fresh water

• More water than Great Lakes

combined

• Deepest (5400’), cleanest and oldest

lake (~25 MY)

• 7th largest surface area (12,250 sq.

mi.)

• Sediment cores go back 6.7 MY

• 330 inlets, one outlet (Angara R.

flows from NW corner)

Midcontinent Rift

• Formed ~1.1 BYA

• Lk. Superior

occupies an

ancient basin in

the rift valley

Icelandic

Rift (Mid-

Atlantic

Ridge)

Connection of BBNP to Pangaea

• 300 MY Ouachita Orogeny > crash between N&S

Am. during creation of Pangaea yielded

continuous belt from BB area, to Ouachita Mtns.,

Appalachians, Canada, Europe, and N. Africa

• BBNP folding and buckling from Farallon Plate,

then Western Interior Seaway sediment

accumulation and Laramide Orogeny ~65 MYA

drove B&R faulting

• Volcanic activity mid-30s MYA and ~15 MYA –

present (common in the west)

~300 MYA

~100 MYA

Pre-Pangaea Collision

Move up earlier and emphasize sect goes from

PC to recent S&G from surrounding erosion and

fill that continues today as mtns. Continue to rise

Simplified valley

stretching model

Listric (normal)

Faults

Graphics from Univ. of

Sydney and Wiki