摘要
本研究利用水下砂箱實驗，模擬海底地下水滲流於大陸邊緣所產生的形貌演化，其中我們控制：(1)流量大小、(2)覆土深度及(3)單點源與雙點源供應等變因，以探索海底峽谷在大陸邊緣出現的機制及成因。
實驗結果顯示，峽谷的出現與否須要達到兩點重要的要素：(1)滲流出的流動必須於峽谷內具有足夠的侵蝕能力；(2)海底地下水需要在坡面底部累積足夠的壓力積聚，如此才能在坡面上形成圓弧狀的峽谷頭部斷面，使得異重流集中在峽谷下切。
此外，實驗結果亦顯示侵蝕的速率會受滲流流量的大小而影響，主要反映在實驗時間長度上。再者，地下水壓力的積聚則是主要受覆土深度這項變因主導，本研究發現在定水頭異重流給的固定壓力下，每一組實驗皆會對應到一個相近的覆土深度。僅有在此覆土深度以下，地下滲流才可自坡面集中形成圓弧狀峽谷斷面並進入滲流峽谷階段。而當覆土深度過大時，坡面會傾向多點的滲出流體造成重力式的崩塌，以達到降低覆土深度的目的。最後，單點與兩點的輸入比較能反映出在各種坡面與流量的條件下，多條峽谷匯聚成單一峽谷地形的趨勢，幫助我們利用峽谷形貌去推測其地下的流體條件。
由於本研究無法獲取水下地下水在土體內實際的滲漏與流動情形，也無法實際掌握峽谷滲流中異重流的流量。使得我們在流量與侵蝕能力的的關聯比較上，有一定程度的誤差。而對水下滲流此研究題目流量的計算與地下水流模式都還未曾開發，因此未來的研究方向若能著重在流量或地下的水流模擬上，能夠使我們對峽谷的成因有更深刻的了解與認識。
關鍵詞：海底峽谷 異重流 海底地下水滲流 大陸棚邊緣 數位影像處理

In this study, we used underwater sandbox experiment to observe the morphologic evolution of the submarine groundwater seepage. We control: the flow rate, the depth of the covering sand and single point source or pair point source supply to explore the cause of submarine canyon growing.
From the experimental results, we found that the development of seepage canyon meet two conditions: (1) The seepage must have sufficient erosion ability, (2) The submarine groundwater needs to accumulate enough pressure at the bottom of the slope. Under this condition, the head of the canyon will appear and the density current will erode.
In addition, the experimental results are also reflected in the variables. First, erosion will be affected by the seepage flow rate, which is reflected in the duration of experiment. Second, we observe that each run will connect with a similar covering depth. Only at a certain depth underground seepage can erupt and form the arc-shaped canyon section, when the depth is thick, the slope will collapse to decrease the covering depth. Finally, pair point source supply can discover the trend of convergence of canyons.
Although we cannot grasp the actual seepage of groundwater, also impossible to obtain the flow rate of the density current in the canyon, we proved that the seepage canyon can developing on experimental slope. If the future research direction focuses on groundwater seepage simulation, it will enable have a deeper understanding of submarine canyon.
Keywords : Submarine canyon, Density currents, seepage, Continental margin.

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