{"id":8033,"date":"2025-07-04T17:49:31","date_gmt":"2025-07-04T17:49:31","guid":{"rendered":"https:\/\/gmcommon.org\/?p=8033"},"modified":"2025-07-04T17:49:37","modified_gmt":"2025-07-04T17:49:37","slug":"myfyrdodau-or-comin-gorffennaf-2025","status":"publish","type":"post","link":"https:\/\/gmcommon.org\/cy\/myfyrdodau-or-comin-gorffennaf-2025\/","title":{"rendered":"Myfyrdodau o’r Comin: Gorffennaf 2025"},"content":{"rendered":"\n
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Trosolwg Byr o Ddaeareg Comin Gelligaer a Merthyr<\/strong><\/h2>\n\n

Pan mae\u2019r haf yn ei anterth, does yno ddim byd prydferthach na Chomin Gelligaer a Merthyr. Gorwedda\u2019r gweundir hwn yng ngogledd Maes Glo de Cymru. O edrych ar y dirwedd, yr hyn sy\u2019n eich taro yw\u2019r meithder dirfawr ac iddo olygfeydd sy\u2019n ymestyn tuag at bellteroedd y M\u00f4r Hafren yn y de a chopa Pen y Fan yn y gogledd. Yn ymwthio o\u2019r tir gwelir ambell i garn fan hyn a fan draw sy\u2019n perthyn i un o gladdgelloedd yr Oes Efydd. Tuag at ogledd y Comin ceir craith fawr lofaol gwaith glo brig Ffos y Fr\u00e2n.<\/strong><\/p>\n\n

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Er gwaetha\u2019r diwydiant glo, y chwareli a\u2019r pentrefi colledig, efallai mai un o\u2019r pethau sy\u2019n ein cyfareddu am y tirlun hwn yw\u2019r ffaith nad ydyw wedi newid rhyw lawer dros y canrifoedd. Mae ei ddaeareg weladwy yn creu pont fetafforaidd rhyngom ni heddiw a\u2019r oes a fodolai ymhell cyn i ddynolryw fodoli hyd yn oed.<\/p>\n\n

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Y Modd y Ffurfiwyd y Glo<\/strong><\/h2>\n\n

Ffurfiwyd yr ehangder gwyrdd hwn, sy\u2019n fyrdd o fywyd gwyllt, amser maith, maith yn \u00f4l. Ffurfiwyd creigiau\u2019r ardal hon rhwng 280 a 340 miliwn o flynyddoedd yn \u00f4l. Mae niferoedd y blynyddoedd mor fawr nes ei wneud yn anodd i\u2019r meddwl ddal gafael arnynt. Enw\u2019r cyfnod hwn mewn hanes yw\u2019r Cyfnod Carbonifferaidd. Mae\u2019r cyfnod hwn yn rhan o\u2019r gorgyfnod Palalos\u00f6ig ac yng Nghymru fe\u2019i diffiniwyd gan y daearegydd (a Deon Llandaf) William Daniel Conybeare ym 1822. Meddai\u2019r daearegydd Dyfed Elis-Gruffydd yn ei lyfr The Rocks of Wales<\/em>: <\/p>\n\n

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\u201cRhennir y cyfnod yn ddau isgofnod, sef y Carbonifferaidd Isaf neu\u2019r Dinantaidd a\u2019r Carbonifferaidd Uchaf neu\u2019r Silesaidd.\u201d<\/p>\n<\/blockquote>\n\n

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Prif nodwedd y cyfnod hwn yng Nghymru oedd ffurfiant y Calchfaen Carbonifferaidd a hefyd \u2013 o ran Comin Gelligaer a Merthyr \u2013 ffurfiant y Cystradau Glo. Weithiau, yn ystod yr ysgrif hon, defnyddir y gair Cystradau Glo. Bryd arall defnyddir y term gwyth\u00efen lo. O ran diddordeb mae Cystraden Lo yn gorff cyfan o graig sy\u2019n cynnwys sawl gwyth\u00efen lo, ymysgu creigiau eraill megis sh\u00e2l a thywodfaen. Yn ne Cymru mae\u2019r cystradau yn drwch o filoedd o droedfeddi. Mae gwyth\u00efen lo, ar y llaw arall, yn disgrifio haenen benodol, denau o lo.<\/p>\n<\/div>\n\n

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Y Comin o dan y M\u00f4r<\/strong><\/h2>\n\n

Ar un adeg roedd y Comin o dan y m\u00f4r ond dros amser trodd y m\u00f4r yn fwy a mwy bas. Yn dilyn y m\u00f4r bu cyfnod lle’r oedd yr ardal hon yn llawn corsydd a fflatiau llaid a oedd wedi eu gorchuddio gyda chyfoeth o lystyfiant anhygoel. Dros amser ffurfiwyd coedwigoedd yn yr ardal hon. <\/strong><\/p>\n\n

Ond gyda threigl a thro\u2019r blynyddoedd, llithrodd yr ardal i\u2019r m\u00f4r unwaith eto a lledaenwyd tywod a mwd dros weddillion y coedwigoedd. O ganlyniad fe\u2019u caewyd yn y ddaear ac fe\u2019i trowyd yn wythiennau glo. O fewn y gwythiennau glo hyn mae toreth o ffosiliau sy\u2019n dangos y math o dyfiant a chreaduriaid a fu\u2019n byw yma ar un adeg: cyndeidiau\u2019r crancod, y misgl a\u2019r chwilod duon mawr. <\/p>\n\n

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Tywodfaen Pennant<\/strong><\/h2>\n\n
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Oherwydd y newidiadau cyson yn lefel y m\u00f4r, ffurfiwyd sawl gwyth\u00efen lo yn ogystal \u00e2 haenau o glai, si\u00e2l a thywodfaen. Ffurfiwyd tywodfaen Pennant yn y modd hwn a dyma\u2019r garreg sy\u2019n rhannu\u2019r wyth\u00efn lo uchaf rhag y wyth\u00efen lo isaf.<\/strong><\/p>\n\n

Gallwch weld olion carreg Pennant led led y cymoedd. Mae hi i\u2019w gweld yn y pentrefi a\u2019r trefi sy\u2019n amgylchynu\u2019r Comin oherwydd dyma\u2019r garreg a ddefnyddiwyd i adeiladu tai hynaf ein hardal. Carreg laslwyd yw hi ond wrth iddi wynebu\u2019r elfennau mae hi\u2019n troi’n frowngoch. Ar Gomin Gelligaer a Merthyr mae ambell i hen chwarel Pennant yn ymwthio o\u2019r tir o hyd. Felly rhwng y glo \u2013 sy\u2019n garreg feddal – mae haenau o garreg galetach y Pennant ac mae\u2019r garreg hon, fwy neu lai\u2019n, creu wal rhwng Fochriw a Bargoed ac un arall rhwng Bedlinog a Threlewis.<\/p>\n\n

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Y Cyfnod Rhewlifol<\/strong><\/h2>\n\n

Yn nes ymlaen daeth y cyfnod rhewlifol pan teyrnasodd amodau Arctaidd dros y rhan fwyaf o ogledd orllewin Ewrop. Pentyrrodd yr eira a throdd hwn yn ei dro yn i\u00e2.<\/strong><\/p>\n\n

Toddodd yr i\u00e2 rhyw 20,000 o flynyddoedd yn \u00f4l a gadawyd cefnau o ro ar hyd y Caiach yn Nelson ac ar hyd y Cylla yn yr ardal lle\u2019r arferai pwll glo Penallta sefyll. Roedd nant Cwm Bargod \u2013 sy\u2019n llifo o Gomin Gelligaer a Merthyr ac i mewn i\u2019r Taf \u2013 yn arfer llifo i lawr at Ystrad Mynach. Un theori am ei gwyriad yw mai rhewlif a rwystrodd llif y nant a\u2019i gorfodi i newid ei hynt a llifo tua\u2019r Taf yn lle. Mae\u2019r Cwm gwag \u2013 am iddo golli ei afon – sy\u2019n cysylltu Nelson ac Ystrad Mynach yn cael ei adnabod, yn ddaearegol yn \u2018fwlch gwynt\u2019.<\/p>\n\n

Nid yw tir y Comin yn edrych yn union fel y\u2019i ffurfiwyd gan y rhewlifoedd. Ers y cyfnod hwnnw bu ambell i dirlithriad. Yn benodol bu cyfres o dirlithriadau mawr yn nwyrain y meysydd glo yn y man lle gorwedda carreg galed y Pennant ar greigiau mwy meddal. Gan fod y graig oddi tan y Pennant yn feddal mae\u2019n erydi\u2019n hawdd a dyma fu\u2019n gyfrifol am y tirlithriadau i mewn i\u2019r cwm. Ceir enghreifftiau o dirlithriadau bach o\u2019r math hwn ger Treodrhiwfuwch a hefyd i\u2019r de o Fochriw. <\/p>\n\n

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Troedrhiwfuwch; y pendtref coll dan fynydd aflonydd<\/figcaption><\/figure>\n\n
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Fast Gelligaer<\/strong><\/h2>\n\n
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Maps atgynhyrchwyd gyda chaniat\u00e2d caredig Arolwg Daearegol Prydain \u00a9 UKRI 2025. Cedwir Pob Hawl.<\/em> Diolch yn fawr iawn i Alan Bowring, Swyddog Datblygu’r Geoparc am fod mor hael gyda’i amser a’i wybodaeth.<\/figcaption><\/figure>\n\n
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Os ydych yn cerdded o faes parcio Pengarn Bugail tua\u2019r gogledd ar hyd y Comin, neu\u2019n teithio ar yr hewl i gyfeiriad Pentwyn o\u2019r de, byddwch yn pasio, ar y chwith, carreg hir yn pwyso ar ei ogwydd i gyfeiriad dwyreiniol. Yn lleol, gelwir y garreg hon y Garreg Waun Hir ac yn \u00f4l yr hanes mae yno filwr Rhufeinig wedi ei gladdi oddi tani. Ond os edrychwch i\u2019r gorllewin, o flaen y Garreg Waun Hir, fe welwch rwyg yn nhir y Comin. Dyma yw Ffawt Gelligaer. Ymlwybra dros y tir i gyfeiriad y gogledd orllewin. Weithiau ymddengys fel cribyn bychan ac os dilynwch ei llwybr, yn nes ymlaen yn yr ardal hon mae\u2019n ymddangos fel hollt. I ddefnyddio disgrifiad y Daearegydd Dyfed Elis-Gruffydd, mae ffawt yn:<\/p>\n\n

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\u201cdoriad mewn dilyniant o greigiau lle mae\u2019r creigiau’r naill ochr a\u2019r llall i\u2019r pl\u00e2n ffawt wedi symud mewn perthynas \u00e2\u2019i gilydd.\u201d<\/p>\n<\/blockquote>\n\n

Yr hyn sy\u2019n brydferth am y ffawt hon yw bod modd i ni ei gweld uwchben y ddaear. I\u2019r glowyr roedd y ffawt yn amlwg iawn o dan y ddaear hefyd oherwydd roedd fel petai\u2019r wyth\u00efen lo\u2019n diflannu. Yn is i lawr, yn y cwm hwnnw a gollodd ei afon, mae Ffawt Gelligaer yn amlygu ei hun ar ffurf clogwyni Penallta. <\/p>\n\n

Cr\u00ebwyd y ffawt hon, ynghyd a\u2019i chwiorydd o fewn Maes Glo De Cymru, rhyw 280-340 miliwn o flynyddoedd yn \u00f4l \u2013 y rhif hwnnw unwaith eto sy\u2019n anodd i ni ei amgyffred. Mae\u2019r ffawt yn gyswllt gweladwy i orffennol mor bellennig nes iddo sefydlu parch ynom at y tir. Hyd yn oed os ydy\u2019r manylion yn celu rhagom, rwy\u2019n meddwl bod rhywbeth y tu fewn i ni gyd sy\u2019n greiddiol ymwybodol ein bod yn ymwneud \u00e2 rhywbeth hynafol wrth inni droedio\u2019r dirwedd hon.<\/p>\n\n

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Bywyd gwyllt a llustufiant ar hyd y ffawt<\/figcaption><\/figure>\n\n\n\n
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Y ffawt ar ei hynt tuag at Ffarm Nant-y-Ffin<\/figcaption><\/figure>\n<\/figure>\n","protected":false},"excerpt":{"rendered":"

Trosolwg Byr o Ddaeareg Comin Gelligaer a Merthyr Pan mae\u2019r haf yn ei anterth, does yno ddim byd prydferthach na Chomin Gelligaer a Merthyr. Gorwedda\u2019r gweundir hwn yng ngogledd Maes Glo de Cymru. O edrych ar y dirwedd, yr hyn sy\u2019n eich taro yw\u2019r meithder dirfawr ac iddo olygfeydd sy\u2019n ymestyn tuag at bellteroedd y […]<\/p>\n","protected":false},"author":8,"featured_media":7939,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_et_pb_use_builder":"off","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-8033","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-newyddion"],"acf":[],"yoast_head":"\nMyfyrdodau o'r Comin: Gorffennaf 2025 – Gelligaer and Merthyr Common<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/gmcommon.org\/cy\/myfyrdodau-or-comin-gorffennaf-2025\/\" \/>\n<meta property=\"og:locale\" content=\"cy_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Myfyrdodau o'r Comin: Gorffennaf 2025 – Gelligaer and Merthyr Common\" \/>\n<meta property=\"og:description\" content=\"Trosolwg Byr o Ddaeareg Comin Gelligaer a Merthyr Pan mae\u2019r haf yn ei anterth, does yno ddim byd prydferthach na Chomin Gelligaer a Merthyr. 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