Pitt Logo LinkContact Us

Eruption and Emplacement Mechanisms and Paleoenvironment of Phreatomagmatic Tephra at Koko Crater Tuff Cone, O’ahu, Hawaii

Simoneau, Elizabeth (2012) Eruption and Emplacement Mechanisms and Paleoenvironment of Phreatomagmatic Tephra at Koko Crater Tuff Cone, O’ahu, Hawaii. Master's Thesis, University of Pittsburgh.

[img]
Preview
PDF - Primary Text
Download (2135Kb) | Preview

    Abstract

    The emplacement processes of proximal tuff cone deposits are often difficult to distinguish. This thesis focuses on the steep outer flank and surrounding apron deposits of Koko Crater, O’ahu, Hawaii. Four sections were logged in detail and interpreted. The steep outer slope deposits are dominated by slumped pyroclastic fallout deposits, some of which may be directly eruption-fed, and minor pyroclastic density current (PDC) deposits, that are rarely slumped. The lack of slumping of the PDC deposits is interpreted as due to their lower eruption volumes, lower depositional rates, lower water content, and longer transport distances, all of which favor more stable slopes. Slumping is also less common on previously slumped substrate, as slumps typically generate a lower gradient than the primary deposits. The occurrence of PDC deposits overlying fallout deposits, may suggest that the PDC deposits were generated by column collapse (partial, sustained or complete). The flanking apron deposits, i.e. those around the base of the steep outer slopes, are dominated by pyroclastic density current, with minor fallout deposits. Slumping is rare in the flanking apron deposits, probably because of the lower substrate gradients. The increasing abundance of PDC deposits with distance from the vent is most likely due to the longer transport distance compared to the ballistic fallout.


    Share

    Citation/Export:
    Social Networking:

    Details

    Item Type: University of Pittsburgh ETD
    ETD Committee:
    ETD Committee TypeCommittee MemberEmail
    Committee ChairSkilling, Ianskilling@pitt.edu
    Committee MemberHarbert, Williamharbert@pitt.edu
    Committee MemberRamsey, Michaelmramsey@pitt.edu
    Title: Eruption and Emplacement Mechanisms and Paleoenvironment of Phreatomagmatic Tephra at Koko Crater Tuff Cone, O’ahu, Hawaii
    Status: Published
    Abstract: The emplacement processes of proximal tuff cone deposits are often difficult to distinguish. This thesis focuses on the steep outer flank and surrounding apron deposits of Koko Crater, O’ahu, Hawaii. Four sections were logged in detail and interpreted. The steep outer slope deposits are dominated by slumped pyroclastic fallout deposits, some of which may be directly eruption-fed, and minor pyroclastic density current (PDC) deposits, that are rarely slumped. The lack of slumping of the PDC deposits is interpreted as due to their lower eruption volumes, lower depositional rates, lower water content, and longer transport distances, all of which favor more stable slopes. Slumping is also less common on previously slumped substrate, as slumps typically generate a lower gradient than the primary deposits. The occurrence of PDC deposits overlying fallout deposits, may suggest that the PDC deposits were generated by column collapse (partial, sustained or complete). The flanking apron deposits, i.e. those around the base of the steep outer slopes, are dominated by pyroclastic density current, with minor fallout deposits. Slumping is rare in the flanking apron deposits, probably because of the lower substrate gradients. The increasing abundance of PDC deposits with distance from the vent is most likely due to the longer transport distance compared to the ballistic fallout.
    Date: 26 January 2012
    Date Type: Publication
    Defense Date: 25 July 2011
    Approval Date: 26 January 2012
    Submission Date: 08 December 2011
    Release Date: 26 January 2012
    Access Restriction: No restriction; Release the ETD for access worldwide immediately.
    Patent pending: No
    Number of Pages: 42
    Institution: University of Pittsburgh
    Thesis Type: Master's Thesis
    Refereed: Yes
    Degree: MS - Master of Science
    Uncontrolled Keywords: phreatomagmatic, tephra, Koko Crater, tuff cone, emplacement
    Schools and Programs: Dietrich School of Arts and Sciences > Geology and Planetary Science
    Date Deposited: 26 Jan 2012 16:13
    Last Modified: 16 Jul 2014 17:04

    Actions (login required)

    View Item

    Document Downloads