著者

有馬 義貴 横山 愛 鳥山 光夫 吉田 早織

出版者

常葉大学浜松キャンパス

雑誌

常葉大学健康プロデュース学部雑誌 = Journal of health promotional sciences (ISSN:21882819)

巻号頁・発行日

vol.13, no.1, pp.21-27, 2019-02-28

著者

石崎 泰男 森田 考美 鳥山 光

出版者

特定非営利活動法人 日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.62, no.3, pp.95-116, 2017-09-30 (Released:2017-10-11)

参考文献数

32

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The ca. 17 cal. ka BP eruption at Nantai Volcano, NE Japan, initially produced widespread Plinian fallout deposit (Nantai-Imaichi Tephra:Nt-I) and two overlying associated scoria flow deposits, i.e., dacitic pyroclast-rich, Shizu Scoria Flow Deposit (SZ) and andesitic pyroclast-rich, Takanosu Scoria Flow Deposit (TKS). A∼2.8m thick outcrop of the Nt-I at Nikko City, 7.5km ESE of the volcano, consists of a basal phreatic fall bed (∼2cm thick) and eleven overlying fall units (units 1-11 in ascending stratigraphic order) defined by componentry, size grading, and chemical composition of the pyroclasts. The total lack of clear boundary structures between each unit suggests that the Nt-I was generated by the pyroclasts falling from continuous eruptive column. Grain size analyses of the Nt-I shows that column height rapidly increased and reached its climax soon after the eruption began, and then oscillated slightly and declined until the end of the Plinian phase. The composition of the pyroclasts shows that the Nt-I resulted from the tapping of a stratified magma chamber, in which dacitic magma capped hybrid andesitic magma. Light-colored, microlite-free, dacitic pumice (DWP) predominates from unit 1 through unit 9. In contrast, moderately vesicular andesitic scoria (AGS) is a major constituent of units 10 and 11. Microlite-rich dacitic obsidian (DOB) is present from unit 1 through unit 3, but was not observed above unit 3. Microlite-rich dacitic scoria (DBS) is present from unit 1 through unit 8, and coexists with DOB in single pyroclast. A plausible explanation for the common eruption of a small amount of microlite-rich pyroclasts along with the predominant DWP is that the microlite-rich pyroclasts represent fragments of the degassed margins of the conduit through which the dacitic magma rose. As the eruption advanced, the passageway may have widened, and the microlite-rich magma along the conduit wall was eroded and ejected along with the DWP. The density of the DWP remained constant from unit 1 through unit 8, and then increased at unit 9. The incorporation of slightly denser, dacitic pyroclast into the column is likely to have destabilized the eruption column. The destabilization caused partial collapse of the column and generated the intra-Plinian Shizu Scoria Flow Deposit, whose particle density is similar to that of unit 9. In contrast, the ejection of dense AGS combined with the incorporation of dense lithics into the eruption column is likely to have destabilized the column, and triggered total column collapse that formed the post-Plinian Takanosu Scoria Flow Deposit.

著者

鳥山 光昭 松元 順 藤嶋 哲男

出版者

日本茶業学会

雑誌

茶業研究報告 (ISSN:03666190)

巻号頁・発行日

vol.1983, no.58, pp.20-27, 1983-12-01 (Released:2009-07-31)

参考文献数

15

被引用文献数

1 2

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有機物施用茶園における,土壌中の可給態窒素含量と収量,品質との関係を明らかにするために,堆肥を6年間毎年0,1,2,4t/10a施用した茶園を供試し,各堆肥施用区のうね間土壌中の無機態窒素濃度を12,24mg/乾土100g(堆肥2t区は24mgのみ)の2段階とし,処理期間における可給態窒素および無機態窒素の含量と収量,品質との相関を求めて比較検討した。その結果は次のように要約される。1) 土壌中の可給態窒素含量は,堆肥施用量を増すほど増加し,4t区では20~22mg/乾土100gで,無施用区の3.6倍に増加した。なお,可給態窒素含量の時期別変動をよ割合に小さかった。2) 一,二番茶期における新芽中の総窒素量は,可給態窒素+春・夏季の無機態窒素の含量との相関が最も高く,可給態窒素と無機態窒素は茶樹の窒素吸収に対する窒素供給源としては,互いに補完的な役割を果しているものと推察された。3) 一番茶の収量は春季の無機態窒素濃度と,二番茶の収量は可給態窒素含量との相関が高かった。一番茶の煎茶品質では各窒素形態の含量との相関関係に有意性は認められなかったが,二番茶の煎茶品質は春・夏季の無機態窒素濃度との相関が高かった。可給態窒素の生産能率は品質よりも収量に対して,また一番茶期よりも二,三番茶期において高いものと推察された。