Geology of Mesa Verde
The geological formations of Mesa Verde National Park were mainly deposited between 100 to 75 million years ago, when
the Western Interior Seaway covered the middle of the continent. During this time, the sea often advanced and retreated,
depositing different types of sediment each time. About 100 million years ago, when the sea first reached the Mesa Verde
area, it depostied layers of sand. Million of years later, this sediment was compacted and cemented into the Dakota Sandstone
Formation which today forms the erosion resistant base beneath the park and Montezuma Valley to the north.
The sea advanced farther westward about 90 million years
ago, and the sandy tidal deposits changed to deep water
shale deposits. The Mancos Shale consists of fine particles
and organic material. Fossils found in this formation include
oysters, clams, shark teeth, and ammonites. The gray
shale forms the low hills you see at the base of the mesa in
the Montezuma Valley. Places to view Mancos Shale: This
formation is best seen from Highway 160 or at the lowest
portion of the entrance road.
Point Lookout Sandstone
Point Lookout Sandstone, deposited as beach sand as the
sea retreated again, is mainly composed of tan to buff colored
sandstone with shale lenses interspersed throughout.
Few fossils are found in this formation. Small alcoves form
in this sandstone layer, but these were not often used by the
Ancestral Puebloans. Places to view Point Lookout Formation:
Point Lookout and the Knife Edge are two geologic
features capped by Point Lookout Sandstone that can be
seen from the entrance road.
After depositing Point Lookout Sandstone, the sea completely
withdrew from the area, leaving a flat, coastal plain.
Swamps developed as small, slow-flowing streams wound
their way to the sea in the northeast. As plant and organic
material decayed and accumulated, dark, fine-grained
shales formed. Thin beds of sandstones and coal seams
can be found within this formation. Leaf impressions, tree
branches, and other fossilized plant remains are located in
the shales. Places to view Menefee Formation: The Menefee
Formation is best viewed from the Geologic Overlook. It
is the layer directly above the Point Lookout Sandstone.
Cliff House Sandstone
The Cliff House Sandstone formation was named for the
Ancestral Puebloan homes built in the alcoves formed
within it. The sea advanced yet again and the influx of sand
generated the thick, orange-buff colored sandstone. Very
few fossils are found in this formation due to tremendous
wave and biological action in the beach environment. The
wave action also generated ripple marks throughout this
layer. Places to view Cliff House Sandstone: This formation
can be seen from any cliff dwelling viewpoint.
|Geologic Column of Mesa Verde National Park|
|Era||Millions of Years Ago||Group||Formation|
|Cretaceous||75||Mesa Verde||Cliff House|
What is a mesa? The word mesa is Spanish for "table." A
mesa is a raised landform that is flat on the top, and has
steep or sloping sides. A plateau is similar, but much larger.
Where did the Ancestral Puebloans get their water?
Rainfall and melting snow soak into and down through
the porous layers of sandstone until the water reaches an
impermeable layer of shale. The process is similar to placing
a sponge (sandstone) on a table (shale) and pouring water
on it. The sponge absorbs the water; but once it is full, the
remaining water seeps through the sponge and pools on the
table. So, prevented from moving down through the shale,
water makes its way sideways through the rock. It eventually
seeps out of the cliff wall and pools to form a small spring.
Seep springs are often found at the base of the Cliff House
Sandstone and Point Lookout Sandstone formations. The
springs provided a source of fresh water for the Ancestral
How do alcoves form? The seep springs created areas
where water accumulated for thousands of years. Over time,
the continuing action of seeping water, freezing and thawing,
wind and rain, broke away the rock and formed alcoves.
Some alcoves became large enough to hold cliff dwellings.
Why are they called alcoves, not caves? Caves are underground
chambers; alcoves are arched openings within
(Information courtesy of the National Park Service)
Copyright © 2003-2006 Calvin & Rosanna Hamilton. All rights reserved.