https://wici.porth.ac.uk/index.php?action=history&feed=atom&title=Tirffurfiau_Ffrwdrewlifol 2026-05-21T20:29:11Z Hanes diwygio'r dudalen hon ar y wici MediaWiki 1.28.0 https://wici.porth.ac.uk/index.php?title=Tirffurfiau_Ffrwdrewlifol&diff=1113&oldid=prev 2014-08-13T15:59:25Z

<p>nodyn ar y drwydded CC</p> <table class="diff diff-contentalign-left" data-mw="interface"> <col class='diff-marker' /> <col class='diff-content' /> <col class='diff-marker' /> <col class='diff-content' /> <tr style='vertical-align: top;' lang='cy'> <td colspan='2' style="background-color: white; color:black; text-align: center;">← At y diwygiad blaenorol</td> <td colspan='2' style="background-color: white; color:black; text-align: center;">Diwygiad 15:59, 13 Awst 2014</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l13" >Llinell 13:</td> <td colspan="2" class="diff-lineno">Llinell 13:</td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>== Llyfryddiaeth ==</div></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>== Llyfryddiaeth ==</div></td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div> &#160;</div></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div> &#160;</div></td></tr> <tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Bennett, M.R. a Glasser, N.F. (ail arg. 2009) ''Glacial Geology: Ice Sheets and Landforms'', Wiley, Chichester, tt. <del class="diffchange diffchange-inline">289-99</del></div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Bennett, M.R. a Glasser, N.F. (ail arg. 2009) ''Glacial Geology: Ice Sheets and Landforms'', Wiley, Chichester, tt. <ins class="diffchange diffchange-inline">289–99</ins></div></td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr> <tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Benn, D.I. a Evans, D.J.A. (adarg. 2010) ''Glaciers and Glaciation,'' Arnold, Llundain, tt. <del class="diffchange diffchange-inline">450-7 </del>a <del class="diffchange diffchange-inline">487-500</del></div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Benn, D.I. a Evans, D.J.A. (adarg. 2010) ''Glaciers and Glaciation,'' Arnold, Llundain, tt. <ins class="diffchange diffchange-inline">450–7 </ins>a <ins class="diffchange diffchange-inline">487–500</ins></div></td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr> <tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Price, R.J. (1973) ''Glacial and Fluvioglacial Landforms'', Oliver &amp; Boyd, Caeredin, tt. <del class="diffchange diffchange-inline">131-77</del></div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Price, R.J. (1973) ''Glacial and Fluvioglacial Landforms'', Oliver &amp; Boyd, Caeredin, tt. <ins class="diffchange diffchange-inline">131–77</ins></div></td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr> <tr><td colspan="2">&#160;</td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr> <tr><td colspan="2">&#160;</td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">{{CC BY-SA}}</ins></div></td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>[[Categori:Daearyddiaeth]]</div></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>[[Categori:Daearyddiaeth]]</div></td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>__NOAUTOLINKS__</div></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>__NOAUTOLINKS__</div></td></tr> </table>

Marc Haynes https://wici.porth.ac.uk/index.php?title=Tirffurfiau_Ffrwdrewlifol&diff=1030&oldid=prev 2014-07-31T11:53:22Z

<p>symudwyd i <a href="/index.php?title=Categori:Daearyddiaeth" title="Categori:Daearyddiaeth">Categori:Daearyddiaeth</a> (yn hytrach na <a href="/index.php?title=Categori:Esboniadur_Daearyddiaeth" class="mw-redirect" title="Categori:Esboniadur Daearyddiaeth">Categori:Esboniadur Daearyddiaeth</a>): h.y. y casgliad daearyddiaeth o fewn yr Esboniadur</p> <table class="diff diff-contentalign-left" data-mw="interface"> <col class='diff-marker' /> <col class='diff-content' /> <col class='diff-marker' /> <col class='diff-content' /> <tr style='vertical-align: top;' lang='cy'> <td colspan='2' style="background-color: white; color:black; text-align: center;">← At y diwygiad blaenorol</td> <td colspan='2' style="background-color: white; color:black; text-align: center;">Diwygiad 11:53, 31 Gorffennaf 2014</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l19" >Llinell 19:</td> <td colspan="2" class="diff-lineno">Llinell 19:</td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Price, R.J. (1973) ''Glacial and Fluvioglacial Landforms'', Oliver &amp; Boyd, Caeredin, tt. 131-77</div></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Price, R.J. (1973) ''Glacial and Fluvioglacial Landforms'', Oliver &amp; Boyd, Caeredin, tt. 131-77</div></td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr> <tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Categori:<del class="diffchange diffchange-inline">Esboniadur </del>Daearyddiaeth]]</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[Categori:Daearyddiaeth]]</div></td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>__NOAUTOLINKS__</div></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>__NOAUTOLINKS__</div></td></tr> </table>

Marc Haynes https://wici.porth.ac.uk/index.php?title=Tirffurfiau_Ffrwdrewlifol&diff=713&oldid=prev 2014-06-19T08:18:52Z

<p>‎<span dir="auto"><span class="autocomment">Llyfryddiaeth: </span>clean up</span></p> <table class="diff diff-contentalign-left" data-mw="interface"> <col class='diff-marker' /> <col class='diff-content' /> <col class='diff-marker' /> <col class='diff-content' /> <tr style='vertical-align: top;' lang='cy'> <td colspan='2' style="background-color: white; color:black; text-align: center;">← At y diwygiad blaenorol</td> <td colspan='2' style="background-color: white; color:black; text-align: center;">Diwygiad 08:18, 19 Mehefin 2014</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l19" >Llinell 19:</td> <td colspan="2" class="diff-lineno">Llinell 19:</td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Price, R.J. (1973) ''Glacial and Fluvioglacial Landforms'', Oliver &amp; Boyd, Caeredin, tt. 131-77</div></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Price, R.J. (1973) ''Glacial and Fluvioglacial Landforms'', Oliver &amp; Boyd, Caeredin, tt. 131-77</div></td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr> <tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[<del class="diffchange diffchange-inline">Category</del>:Esboniadur Daearyddiaeth]]</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[<ins class="diffchange diffchange-inline">Categori</ins>:Esboniadur Daearyddiaeth]]</div></td></tr> <tr><td colspan="2">&#160;</td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>&#160;</div></td></tr> <tr><td colspan="2">&#160;</td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins class="diffchange diffchange-inline">__NOAUTOLINKS__</ins></div></td></tr> </table>

Marc Haynes https://wici.porth.ac.uk/index.php?title=Tirffurfiau_Ffrwdrewlifol&diff=346&oldid=prev 2013-12-03T14:35:17Z

<p></p> <table class="diff diff-contentalign-left" data-mw="interface"> <col class='diff-marker' /> <col class='diff-content' /> <col class='diff-marker' /> <col class='diff-content' /> <tr style='vertical-align: top;' lang='cy'> <td colspan='2' style="background-color: white; color:black; text-align: center;">← At y diwygiad blaenorol</td> <td colspan='2' style="background-color: white; color:black; text-align: center;">Diwygiad 14:35, 3 Rhagfyr 2013</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l18" >Llinell 18:</td> <td colspan="2" class="diff-lineno">Llinell 18:</td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr> <tr><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Price, R.J. (1973) ''Glacial and Fluvioglacial Landforms'', Oliver &amp; Boyd, Caeredin, tt. 131-77</div></td><td class='diff-marker'>&#160;</td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Price, R.J. (1973) ''Glacial and Fluvioglacial Landforms'', Oliver &amp; Boyd, Caeredin, tt. 131-77</div></td></tr> <tr><td colspan="2">&#160;</td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr> <tr><td colspan="2">&#160;</td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">[[Category:Esboniadur Daearyddiaeth]]</ins></div></td></tr> </table>

Elis Glynne https://wici.porth.ac.uk/index.php?title=Tirffurfiau_Ffrwdrewlifol&diff=75&oldid=prev 2013-08-29T13:22:44Z

<p>Crëwyd tudalen newydd yn dechrau gyda &#039;(Saesneg: &#039;&#039;fluvioglacial landforms&#039;&#039;) Y tu hwnt i derfynau <a href="/index.php?title=Llenni_i%C3%A2&amp;action=edit&amp;redlink=1" class="new" title="Llenni iâ (does dim tudalen o'r enw hwn i gael)">llenni iâ</a> (&#039;&#039;ice sheet&#039;&#039;) a rhewlifau mae afonydd a nentydd allolchi (&#039;&#039;outwash&#039;&#039;), a gy...&#039;</p> <p><b>Tudalen newydd</b></p><div>(Saesneg: ''fluvioglacial landforms'')<br /> <br /> Y tu hwnt i derfynau [[llenni iâ]] (''ice sheet'') a rhewlifau mae afonydd a nentydd allolchi (''outwash''), a gyflenwir gan ffrydiau o ddŵr tawdd uwchrewlifol, mewnrewlifol a thanrewlifol, yn gyfrifol am ddyddodi’n gyflym drwch o waddodion ffrwdrewlifol (haenau o raean a thywod yn bennaf) sy’n esgor ar dri grŵp o dirffurfiau allolchi, sef (i) bwâu allolchi (''outwash fans'') a gwastadeddau allolchi (''outwash plains'') sy’n nodweddu’n bennaf y rhagdiroedd rhewlifol (''glacial forelands'') heb gyfyngiadau topograffig; (ii) terasau ffrwdrewlifol (''kame terraces'') a chnyciau gro (''kames'') sy’n nodweddu’n bennaf ddyffrynnoedd mwy cyfyngedig; a (iii) esgeiriau (''eskers'') sy’n nodweddu dyffrynnoedd eang a rhagdiroedd.<br /> <br /> Mae bwâu allolchi’n ymgrynhoi o flaen terfyn rhewlif neu len iâ sefydlog ac yn y mannau hynny lle mae ffrydiau o ddŵr tawdd yn ymarllwys o ben blaen y corff iâ. Ond wrth i ddau neu fwy o fwâu gyfuno â’i gilydd esgorir ar wastadeddau allolchi (sandurau) a nodweddir gan systemau cymhleth o [[afonydd plethog]] (''braided rivers''), ynghyd ag olion hen sianeli a barrau. Weithiau, y mae i’r rhan honno o fwa sydd agosaf at derfyn yr iâ, sylfaen sylweddol o iâ llonydd claddedig (''buried dead ice'') ac os yw hwnnw’n dadmer wedi i lif yr afon a greodd y bwa sychu, trawsnewidir arwyneb cymharol lyfn y bwa yn ddrysfa o gnyciau a phantiau, gan ffurfio topograffi cnwc a phant (''kame and kettle topography''). Fodd bynnag, yn absenoldeb haen sylweddol o iâ claddedig, dim ond ambell bant iâ llonydd (''kettle hole'' – pant sy’n ymffurfio wrth i gorff o iâ ddadmer a’r gwaddodion oddi amgylch iddo gwympo) a fyddai’n ymddangos ar arwyneb y bwa. At hynny, os pery llif yr afon sy’n cyflenwi gwaddodion y bwa wedi i’r iâ claddedig lwyr ddiflannu, ni fyddai fawr ddim tystiolaeth o ymsuddiant (''subsidence'') yn ymddangos ar arwyneb y bwa, er y byddai’n amlwg ar ffurf adeileddau gwaddodol (''sedimentary structures'') oddi mewn i’r gwaddodion allolchi. <br /> <br /> Ar loriau dyffrynnoedd, gall gwaddodion allolchi ymgasglu ar ffurf terasau ffrwdrewlifol y naill ochr a’r llall i ran flaen rhewlif enciliol, yn enwedig os yw’r iâ’n gymharol lonydd. Mae maint teras ffrwdrewlifol yn dibynnu’n bennaf ar faint yr afon ddŵr-tawdd ochrol, sy’n cyflenwi’r gwaddodion allolchi, ac ar ongl y llechwedd y mae’r rhewlif yn rhannol orwedd arno. Felly, os yw’r afon ddŵr-tawdd ochrol yn fawr a llechweddau’r dyffryn ar oleddf cymedrol bydd y teras a ddaw i fod, o ganlyniad i’r ddadmer iâ ochrol claddedig, yn esgor ar gadwyn o bantiau iâ llonydd ar hyd wyneb blaen y teras. Yn absenoldeb y fath gadwyn amlwg o bantiau iâ llonydd gall gweddillion arwyneb llain ddyranedig o waddodion allolchi (llain dyffryn [''valley train'']) gael eu camgymryd am derasau ffrwdrewlifol.<br /> <br /> Twmpath neu fryncyn unigol o waddodion haenog ffrwdrewlifol yw cnwc gro (''kame''). Yn achos nifer ohonynt, mae’n ymddangos fod y gwaddodion wedi ymgasglu ar waelod siafftiau dŵr tawdd (''moulins'') a chrefasau, ond gall eraill gynrychioli crynoadau o waddodion a ddyddodwyd hwnt ac yma ar welyau afonydd uwchrewlifol ac a gafodd eu graddol ostwng ar wely’r rhewlif o ganlyniad i ddarfodiant yr iâ llonydd.<br /> <br /> Yn wahanol i gnyciau gro, y gred yw y caiff y rhan fwyaf o esgeiriau eu dyddodi gan afonydd dŵr tawdd yn llifo drwy dwneli tanrewlifol a bod cyfeiriadaeth y cefnennau dolennog hyn, sy’n cynnwys tywod a graean lled annidoledig (''poorly-sorted'') ac o bosibl orchudd tenau o dil, yn cyfateb i gyfeiriad llif yr iâ. Eto i gyd, ni ddylid diystyru’r posibilrwydd fod rhai esgeiriau, a all fod ar ffurf cefnennau unigol neu rwydweithiau o gefnennau plethog, yn cynrychioli systemau draenio mewnrewlifol ac uwchrewlifol. Yn wir, mae arsylwadau yng Ngwlad yr Iâ yn awgrymu y gall gwaddodion ffrwdrewlifol sy’n llenwi twneli mewnrewlifol a sianeli uwchrewlifol gael eu gostwng a’u harosod ar wely rhewlif o ganlyniad i enciliad a darfodiant yr iâ. Ar ben hynny, mae awduron eraill o’r farn fod ambell esgair yn datblygu wrth i afon ddŵr-tawdd danrewlifol ddyddodi llwythi o waddodion ffrwdrewlifol o flaen trwyn rhewlif neu len iâ sy’n prysur encilio. Mae’r fath esgeiriau wedi’u cyffelybu i ddeltâu hirgul a ddatblygodd ar ongl sgwâr i derfyn yr iâ.<br /> <br /> == Llyfryddiaeth ==<br /> <br /> Bennett, M.R. a Glasser, N.F. (ail arg. 2009) ''Glacial Geology: Ice Sheets and Landforms'', Wiley, Chichester, tt. 289-99<br /> <br /> Benn, D.I. a Evans, D.J.A. (adarg. 2010) ''Glaciers and Glaciation,'' Arnold, Llundain, tt. 450-7 a 487-500<br /> <br /> Price, R.J. (1973) ''Glacial and Fluvioglacial Landforms'', Oliver &amp; Boyd, Caeredin, tt. 131-77</div>

Gwydion Jones