Environmental Implication of Subaqueous Lava Flows from A Continental Large Igneous Province: Examples from the Moroccan Central Atlantic Magmatic Province(CAMP)

The Early Jurassic volcanic sequence of the Central Atlantic Magmatic Province(CAMP)of Morocco is classically subdivided into four stratigraphic units:the Lower,Middle,Upper and Recurrent Formations separated

The Qixiangzhan Lava Flow at the Tianchi Volcano:Eruptive Dynamics,Emplacement Mechanism and Implications for the Formation of Long-lived Magmatic Systems Prior to Caldera-forming Eruptions

The 7 ka old Qixiangzhan lava flow(QXZ,Tianchi volcano)represents the last eruptive event before the 946 CE,caldera-forming‘Millennium’eruption(ME).Petrographic,whole rock,mineral composition,Sr-Nd isotopic data on QXZ show that:(a)the lava consists of two components,constituted by comenditic obsidian fragments immersed in a continuous,aphanitic component;(b)both components have the same geochemical and isotopic variations of the ME magma.The QXZ and ME comendites result from fractional crystallization and crustal assimilation processes.The temperature of the QXZ magma was about 790℃ and the depth of the magma reservoir around 7 km,the same values as estimated for ME.QXZ had a viscosity of 10^(5.5)-10^(9) Pa s and a velocity of 3-10 km/yr.The emplacement time was 0.5-1.6yr and the flow rate 0.48-1.50 m^(3)/s.These values lie within the range estimated for other rhyolitic flows worldwide.The QXZ lava originated through a mixed explosive-effusive activity with the obsidian resulting from the ascent of undercooling,degassing and the fragmentation of magma along the conduit walls,whereas the aphanitic component testifies to the less undercooled and segregated flow at the center of the conduit.The QXZ lava demonstrates the extensive history of the ME magma chamber.

Conifer establishment after the eruption of the Paricutin volcano in central Mexico

Background:Volcanic eruptions have large effects on forest ecosystems and create new substrates,triggering primary succession processes.The Paricutín volcano,born in central-western Mexico,erupted between 1943 and 1952.After the cessation of the eruptive activity,plant colonization began on the lava flows and tephra deposits,including the conifer species that dominate the surrounding mature forests.This study aims to reconstruct the history of the establishment of conifer trees on the substrates created by the Paricutín eruption.Methods:16 sampling plots were established along three transects with northern,southern,and south-western aspects,located every 250 m from the preserved forest to the volcanic cone.Increment cores from 400 conifer trees were extracted and their age was determined by cross-dating annual tree rings.The order of the species colonization and the tree establishment,abundance,and dominance patterns were characterized.Also,the influence of the distance from the mature forests and the inter-annual climatic conditions on the temporal tree establishment pattern was evaluated.Results:Eight pine and one fir species have been established since 1970,only 18 years after the end of the eruptive period.However,tree establishment increased by 12.9%annually after 1995,with the youngest tree in our sample getting established in 2015.We did not find a well-defined temporal and spatial pattern of species arrival,which suggests that colonization occurred randomly,although the four pine species that were established early became the most abundant and dominant.Tree establishment was not influenced by the distance from the mature forest,and wet inter-annual conditions did not enhance pulses of tree recruitment,exhibiting a continuous tree establishment pattern.Conclusions:Conifer species have shown a great capacity for colonizing volcanic substrates created by the Paricutín eruption,which suggests that tropical montane conifers can regenerate rapidly under high-magnitude disturbances.These findings support the use of these forest species for ecological restoration.