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R. A. De Hon
2011 SWAAG, Austin, TX
CRATER MORPHOLOGIES IN MONOGENETIC VOLCANIC FIELDS OF WESTERN
NEW MEXICO
THIS PRESENTATION
• As title states…
Morphology of landforms in three monogenic volcanic fields in western New Mexico
• Specifically, the morphology of… Maar craters Tuff rings Cinder cones
and modification of these forms
• Located in …
Red Hill-Quemado Volcanic Field Bandera Volcanic Field Mt. Taylor-Mesa Chivato Volcanic Field
Mesa Chivato
Bandera (Malpias)
Red Hill MAAR CRATERS
Ariz
ona
New
Mex
ico
WITH SPECIAL ATTENTION TO MAAR CRATERS
• Maar craters are formed when magma encounters groundwater. The resultant venting to the surface excavates a bowl-shaped pit surrounded by a tuff ring that resembles a meteorite crater.
• The term maar comes from a Franconian dialect for lake derived from the Latin “mare” (sea).
• In the type locality—the Efiel Region of Germany— the craters extend below the water table and are occupied by lakes.
• Maar craters range in size from a few hundred meters to several kilometers in diameter.
• Their eruptive history consists of repeated venting over a period of weeks or months.
ULTIMATE OBJECTIVES
• Volcanic morphometry with attention to craters and their modification by later eruption or erosion
• Early ejecta as sampling of subjacent rock materials
• Application to Martain volcanic craters.
WHY SHOULD YOU CARE?
• The earliest ejecta in maar craters provide a sampling of subjacent strata.
• At some localities the ejecta incudes mantle xenoliths.
Mantle XenolithKilbourne Hole, NM
ZUNI SALT LAKE
1 km
Rim deposits
Air Fall Lapilli Tuff, Zuni Salt Lake Maar
Base surgeand Air Fall
Vent Opening Breccia
Breccia contain blocks of subjacent rocks including basement granites and in some localities mantle xenoliths
Base Surge and Air Fall Bedded Deposits
Vent Opening Breccia
RIM DEPOSITS AT KILBOURNE HOLE
Base Surge Beds
Bomb Sag
Accretionary Lapilli
This study
N
100 km
Location of volcanic vent structures in western New Mexico
CHAIN OF CRATERSBANDERA FIELD
Maar
Malpais
CERRO AMERICO
EXAMPLE: CINDER CONE—CERRO AMERICO
Basal Diameter 1 237 metersCrater Diameter 269 Cone Height 118 Crater Depth 41
BANDERA CRATER
EXAMPLE: TUFF RING—BANDERA CRATER
Basal Diameter 1156Crater Diameter 556Rim Height 128Crater Depth 156
HUECO CRATER
EXAMPLE: MAAR—HUECO CRATER
Basal Diameter 1150 metersCrater Diameter 718Rim Height (h) 75Crater Depth (d) 98
dh
La Jolla Maar, Mesa Chivato
1 km
Many maare in the region are characterized by concentration of scrub vegetation on raise tuff rings.
LA JOLLA MAAR, MESA CHIVATO
Basal Diameter 1200Crater Diameter 930Rim Height 15Crater Depth 36
Scoria mound
Tuff Rings
Depth vs. Height
PRISTINE
Tuff Ring
Maar
Cinder cone
VOLCANIC CENTRAL VENT VARIATIONS
1 km
All profiles to same scale.
Variation in size and morphology is chiefly due to the duration of eruptions and volume of material ejected.
Composition of ejecta changes as eruption progresses…
Lava
Scoriaceous cinders
Epiclastic bedded tuff
Early xenolith-rich breccia
VENT MORPHOLOGY
•Magma and ground-water interaction
•Duration of activity
• Accidental ejecta
• Pyroclastic
• Lava
•Resistance of country rock• Slumping during eruptive phase
• Degradation following eruption
Highly eroded -or-Blew its top?
Floor above surface
Nested Craters
RED HILL MAARMaar with floor cinder cones
Cone filling maar
Rimless depression(erosional remnant
of maar crater)
Renewed activity Pristine Degraded
Cone filling maar Tuff Ring Breached crater
Cone-in-maar Maar Rimless depression
Explosion crater? Cinder cone Scoria Mound
VOLCANIC CENTRAL VENT VARIATIONS
1 km
All profiles to same scale.
Morphological variations corresponding to renewed eruptions or by erosional degradation
SO, WHAT? THE POINT IS…
• Earliest maar ejecta provides a sample of substrate materials.
• Those early materials may be preserved in a variety for subsequent volcanic structures.
• Someday…maar craters and their variants will be important sites to visit on Mars.
CREDITS PREVIOUS WORKERS IN WESTERN NEW MEXICO VOLCANIC FIELDS
• Jayne C. Aubele
• Larry S. Crumpler
• A. W. Laughlin
• P. W. Lipman
• C. Maxwell
• And many others
Mars Volcanic field
THANK YOU