Emplacement of xenolith nodules in the Kaupulehu lava flow, Hualalai Volcano, Hawaii

210

174

Abstract. Long basaltic lava flows (over 100 km in length) require specific emplacement conditions to prevent the lava from freezing as it is transported to the flow front. The minimum dimensions of the lava transport systems (tubes, channels, or sheets) require that the flow have a volume greater than several cubic kilometers. Long lava flows are emplaced on slopes less than 10% (•-5 ø) and the lava being transported must cool at a rate less than 0.5øC/km. We show that there are two modes by which thermally efficient, long distance lava transport can be achieved: (1) "rapid" emplacement in which the lava flows so quickly that it does not cool excessively despite large heat losses and (2) "insulated" emplacement in which heat loss is minimized. We here estimate cooling in the rapid mode using a modified version of a previously published thermal model for aa flows and find that, for a range of inputs appropriate for subaerial terrestrial condition, eflhsion rates of at least 3100 to 11000 m3/s, channel flow velocities in excess of 4 -12 m/s, and minimum channel depths of 3 -17 rn are required for basaltic flows > 100 km in length. For emplacement in the insulated mode, we construct a very simple heat balance model for roofed sheet flows which shows that extremely long sheet-fed flows are possible with velocities as low as 0.2-1.4 m/s, flow thickness of 6 -23 m, and minimum effusion rates of the order of 50 -7100 m3/s. Also, earlier work has suggested that tube-fed flows more than 100 km long can be produced at effusion rates as low as several tens of m3/s and with tube diameters of a few tens of meters. We argue that flows emplaced in the rapid mode should be morphologically similar to channel-fed aa flows while those emplaced in the insulated mode should be similar to tube-fed or sheet-like inflated pahoehoe flows. This leads to several field criteria for distinguishing these two modes of emplacement in ancient lava sequences. Additional constraints on the emplacement of long lava flows are expected from the continued study of the formation and evolution of lava channels, tubes, and sheets.

Section: Expected Flow Morphologysupporting

confidence: 50%

Some physical requirements for the emplacement of long basaltic lava flows

Keszthelyi¹,

Self²

1998

210

174

“…Streamlines within the distal zone exhibit circulation, time dependence, and randomness. The host of complicated processes as described by Guest et al [1987], Lipman and Banks [1987], Moore [1987], Guest et al [1995], and Glaze and Baloga [2006] that occur near the front make a detailed deterministic treatment impossible. Here we do not worry about the details of levee formation, only that some volume of active lava becomes stationary in the distal zone.…”

Section: Self‐replication Modelmentioning

confidence: 99%

“…Stationary margins of long channelized lava flows do not always form solely in the frontal zone. Another significant mechanism for forming stationary margins is through overspills and breakouts [e.g., Guest et al , 1987, 1995; Lipman and Banks , 1987; Moore , 1987; Baloga et al , 2003; Hon et al , 2003; Rowland et al , 2004; Glaze and Baloga , 2006; Woodcock and Harris , 2006; Garry et al , 2007]. These occur upstream in the channel zone when the flow stagnates, the channel becomes clogged, a levee collapses, or there is a surge in the supply rate.…”

Section: Influence Of Overspillsmentioning

confidence: 99%

“…Others crudely estimate how the levees or stationary margins grow. It is well known from terrestrial experience that the process of levee and stationary margin construction is extremely complicated, time‐dependent, and subject to a host of random effects [ Lipman and Banks , 1987; Moore , 1987; Guest et al , 1987, 1995; Baloga et al , 1998; Hon et al , 2003; Glaze and Baloga , 2006]. From a modeling perspective, the main concern is how the lava volume is conserved, i.e., where and when lava volume transitions from actively participating in the flow advance to a passive role, perhaps confining the active component.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A self‐replication model for long channelized lava flows on the Mars plains

Baloga

Glaze

2008

Self Cite

[1] A model is presented for channelized lava flows emplaced by a self-replicating, levee-building process over long distances on the plains of Mars. Such flows may exhibit morphologic evidence of stagnation, overspills, and upstream breakouts. However, these processes do not inhibit the formation and persistence of a prominent central channel that can often be traced for more than 100 km. The two central assumptions of the self-replication model are (1) the flow advances at the average upstream velocity of the molten core and (2) the fraction of the lava that travels faster than the average upstream velocity forms stationary margins in the advancing distal zone to preserve the self-replication process. For an exemplary 300 km long flow north of Pavonis Mons, the model indicates that $8 m of crust must have formed during emplacement, as determined from the channel and levee dimensions. When combined with independent thermal dynamic estimates for the crustal growth rate, relatively narrow constraints are obtained for the flow rate (2250 m 3 s À1 ), emplacement duration (600 d), and the lava viscosity of the molten interior (10 6 Pa s). Minor, transient overspills and breakouts increase the emplacement time by only a factor of 2. The primary difference between the prodigious channelized Martian flows and their smaller terrestrial counterparts is that high volumetric flow rates must have persisted for many hundreds of days on Mars, in contrast to a few hours or days on Earth.

“…Guest et al [1995] have attributed the high rate of discharge to the near-Newtonian rheologic properties of the host lava during both eruption and emplacement. Guest et al [1995] have attributed the high rate of discharge to the near-Newtonian rheologic properties of the host lava during both eruption and emplacement.…”

Section: /3 Cf 0) 1/3 (11)mentioning

confidence: 99%

The dynamics of rapidly emplaced terrestrial lava flows and implications for planetary volcanism

Baloga¹,

Spudis²,

Guest³

1995

The Kaupulehu 1800–1801 lava flow of Hualalai volcano and the 1823 Keaiwa flow from the Great Crack of the Kilauea southwest rift zone had certain unusual and possibly unique properties for terrestrial basaltic lava flows. Both flows apparently had very low viscosities, high effusion rates, and uncommonly rapid rates of advance. Ultramafic xenolith nodules in the 1801 flow form stacks of cobbles with lava rinds of only millimeter thicknesses. The velocity of the lava stream in the 1801 flow was extremely high, at least 10 m s−1 (more than 40 km h−1). Observations and geological evidence suggest similarly high velocities for the 1823 flow. The unusual eruption conditions that produced these lava flows suggest a floodlike mode of emplacement unlike that of most other present‐day flows. Although considerable effort has gone into understanding the viscous fluid dynamics and thermal processes that often occur in basaltic flows, the unusual conditions prevalent for the Kaupulehu and Keaiwa flows necessitate different modeling considerations. We propose an elementary flood model for this type of lava emplacement and show that it produces consistent agreement with the overall dimensions of the flow, channel sizes, and other supporting field evidence. The reconstructed dynamics of these rapidly emplaced terrestrial lava flows provide significant insights about the nature of these eruptions and their analogs in planetary volcanism.