CINXE.COM
Just a moment...
<!DOCTYPE html><html lang="en-US"><head><title>Just a moment...</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=Edge"><meta name="robots" content="noindex,nofollow"><meta name="viewport" content="width=device-width,initial-scale=1"><style>*{box-sizing:border-box;margin:0;padding:0}html{line-height:1.15;-webkit-text-size-adjust:100%;color:#313131;font-family:system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,Noto Sans,sans-serif,Apple Color Emoji,Segoe UI Emoji,Segoe UI Symbol,Noto Color Emoji}body{display:flex;flex-direction:column;height:100vh;min-height:100vh}.main-content{margin:8rem auto;max-width:60rem;padding-left:1.5rem}@media (width <= 720px){.main-content{margin-top:4rem}}.h2{font-size:1.5rem;font-weight:500;line-height:2.25rem}@media (width <= 720px){.h2{font-size:1.25rem;line-height:1.5rem}}#challenge-error-text{background-image:url(data:image/svg+xml;base64,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);background-repeat:no-repeat;background-size:contain;padding-left:34px}@media (prefers-color-scheme:dark){body{background-color:#222;color:#d9d9d9}}</style><meta http-equiv="refresh" content="390"></head><body class="no-js"><div class="main-wrapper" role="main"><div class="main-content"><noscript><div class="h2"><span id="challenge-error-text">Enable JavaScript and cookies to continue</span></div></noscript></div></div><script>(function(){window._cf_chl_opt={cvId: '3',cZone: "pubs.geoscienceworld.org",cType: 'managed',cRay: '91809197ed6a48d6',cH: '.r6orptEo3GE26ocIqWiPrCq6vCZLOtyIhzVUFdTVjc-1740579552-1.2.1.1-6yamrXn27aqLZNRu_mVvMaGrqTvbvlM3mOesInQdmpfzg5tEM2AUCbvzaRJXhWA1',cUPMDTk: "\/geology\/article\/31\/1\/47-50\/192515?__cf_chl_tk=AfbjJxwGfIsTH97TiP48mmmoofPUsJuQGXxt051W5wI-1740579552-1.0.1.1-dgUSPkVz9I4pZzL7QPPZ.UUQDY_XMqO7HkSQQ60d8a0",cFPWv: 'b',cITimeS: '1740579552',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/geology\/article\/31\/1\/47-50\/192515?__cf_chl_f_tk=AfbjJxwGfIsTH97TiP48mmmoofPUsJuQGXxt051W5wI-1740579552-1.0.1.1-dgUSPkVz9I4pZzL7QPPZ.UUQDY_XMqO7HkSQQ60d8a0",md: "OwyDbQCAvat.an3f65iO677Mlnerfx0mZPf3w97gbLE-1740579552-1.2.1.1-HjCMUVxN_Ds3kms5BwEU9C8m8aV0ATwptuETgGScB6W_Mm0xThxj_POFm72XFMA6Ze.n84mrBgHvbR2rHqkMZxWlqI826kZpRJpcNfg2Tfq7h62Inoly.byxdXzZq4sa5_WTWfDFFAtamsZL9GiCpLlxggaAOTrW4jx49Dhn352ABdR27LPCEd3CnbsO.T7rM2Stuym7cTr2MsrhBeHr7eObc8aagaRl6eP3Jf9fs282E6ug_zFRalyNqEHKrFUQXSE8Jz_WTtk88aVK28gGEUX8JOc8pJ1ZN.0wxmMbMVWZgqzHeLPEDTmmvc4FdlKCuAhEMOurqjs.y7cF76z3f58Rm2C.FlayjGWcKQibv8Q_zQhw.N5lUXFZtIjd4kTPxt.1c1hc30WQidyA4OFCw6_KIar8UHthOKLWiKlCt38g.1EF1hr4DgH2FcI2bMwv7AsVHV1qMZ6LvOAaP8YYPYx4ST4J2tCn..8MJlNkAgnwMrS4dI3.KYAJVX66BGEdR5J7PU519zrygcPAGwHnerSnNtnmISUL8bFr_xZmgDK2vYvHZ5t7WsZWPkRUHTPXR.wgt.2c3k6UyczwuUb0j1Sm2suQ2UWizmcdvFvgqm7zK.zQ1q8UUuZOLOPaFMYF0D3pPVwe9ginx5l3rx3j3yVvYex9rw.7tCb12lQi91nMMn.CkXRvhMPvhi5jVr4cajvHDu.LVmM6ICUrHGU.I.Gy_QRPCJPl5olVwqxYdKYqqZ4TMMHLK3OgS7piioZwwaFICaAdgmbfz6eaF7hH.49rMbbRNLir2f5x7.V3ixGL6dhGse5UhPsZ9y3KC_QGENRIDBpuh3FngObZXom5w4CX9r.Hx0.OyP9hh_Jzh.ucMEgZlDETwntuvc14yqU8tBvUlPJLyyQ1.LIXOru15Oaj8GT6_kKY2Ww4B9cBm_ASW96qoFMHVz_fuUWPmewM9UWV01dyckzNx9WHb5VQc9a57EPYXClcfjUj3AAaWhkEbyn2Vj6fI3BIxXpxfNTQqYVaI5zFknUpNcx1s8iUh1gNEOMh0lu5cV5Q_YZXYv7dHKLc2oeMS8svD770tsNTcwwtxyFyf05scVJr4MFUwsHQPBuGZlCLq8RJJJQu3VJe2ca26V97Vf2crLwFgi5QNARfxOF6sMKHwqTtFuuQDa21Pi_NL.XBNMoLRH55aspxK3CC9hjjwd8X1ylzIxUtLOik3X7Mmbq.bc6ltiThZWBxIHzx8ZGNzd19BlJzT7YVTW32IHKS.w3JEPSB4adupveeLx7tMsOO8AdqCEQjHSLsEEmnaSDRIYIo4EbFYx9EveCCOwCOtW_1qJnMjxLpviWdG0sR6XVMJxI4U_SbJsd0AswvX61d_AA_.oEVFNPXpG14yQj7NCBugU860_8tCif0_cYkeA8zCR6p1nWyvv5rNK1qAG2S4a1AogX.Mds5.k6ZmaOoeFE9mjgIckhMuN5LwJY.p2hnVWX2_e_vgzBZkfd9VywU2yDE_DX8AUDgvnYRfh9NBc.7OyF98GlfHOXaPDFoIDIONLap5gYqF_3Pb7lXbWsW9THBAnfetCzhl_w0mzbIb2EcjmVH2ProBmrQC5bedpodywBlBOGyUB9NR4KF3KNv5DF3T0UUpWBsrn7CBZQZQkaA8zWiZcvXjiD__MEjK.y8DIZtq8MxgLFPsvxcq.k8_TBjr5mwuiENF7CnSIlFHwTlBaSvJ1CsCXFaE6A1u44x_HDruCepr_q4uJSjljANdWHOI5a3LoimJmlLGorlqxwtWDG5MlK4G8_.P7SpiTNktGXDYIh2Sg4sauvDcA18OttKk.nf367aJYIEJMdee_wmgvOT3uh3G5U735IWRX_wluXbpf7gU4mH1weov9DdWCf1z9sARhRvtJPAND4KtunxqIk2IeRSG4QyuJUjsrKI1_k.dSu2Te9ruWRLJAgQ.pYQAf5n744bk4YmLgJuBvyVfkpq_QZLZFbi0yz8t6hWgGMcVVzzIf8sOSJHNqfCOyERt65XyKh6.Yn2zsn7xLlnn4SvkbbhL2NW05U2siQH.TB3EzAhNijZhWGtzQ0J1zx5nJT9l36z4ATJPrVY9199V0TMHyxk_BhCOfx7jzag._SKEMcLgHNkvq7wwCq2.e12JndRpJmjrQz.hMPy7NehGR8avj7iymlVV7qj4Mz2e8j75fOq4n3A2U5l2NnZGwnsAKX5Ld9efHv64Kzh4rm5mZ8DMFdxV8CH18Plhqzxsem4ttxKyRhdYRdwZLyPzpjfIIvFlV_4EQXAqT2jWBivf5daCdB.TuaB7Rj2F0cWR4pehobNwTI68cZy17ZGa.eyk51agzDXPbdwSburW62m8O.qf..uniO4m8e2Nalusk9rz6jM2FOw0Fvf1ogqbG3vbg.g9GVcfWcumWNBH_iGDkFK6lYYsREVH1T21Whad_dvB295scHf5iFZrCagd9BebmeuuMfy7GPMAkE4ez71ADONeOtayE69soYRVvnEr9SeDA29hXvWRfGMIkVurnWUsTa23e0uaxWOp_JST4mZdgeiSTMRa.xZDfa3qwIlqwSjQcKJVufsbyJu9AUYnjWzVFozRKOnPuZ7IzZxvoBtXsuhZwsX",mdrd: "RqPvhfEjLEy1WNIGm1bzDGizFBa3LDwQEDCR4u_2PbY-1740579552-1.2.1.1-FspNEW7U8W16bWV9dg_CJThympAvxxV0zXHV4gdCiWSjWL_yuAP2MJcuY5C5KAS5rwnd7bDSy.JLs00Pt0cZpziaVPTzvTAwPuymc.9fdXLqzZRk8fkeAk7z4yn11h6ENAMpNTr7.OkJqJITswO.TjhS.VTyA6ZL2UMBQAXgMwvFUTZbroq.MGl7PdSAgKuZZWzFeCINi5i2gXtNa04ZGQYCHKwlBNfbgj_foFjtZIy_V0RJZxjlKYEC4V5TtIUSQzPCQjIt.sm_bFf2d3ElBTirWyPMcuzWO5XI34lyYNHZ_jZhSWQicOlF5YkM8dsp3QiMMi1MDSCthilyJNKuzKoU6Qf7EssWuu_M4.NBttAhvYSWF4XT4bS43fP4eKbqtf0m_5.48xrZMYKS7IUzyDfgc31Na5I9uGUCLDRibBot81SxwpKOHZvzUieMq3tNRjMbilE5ciwt9Ya73yFXSPrHeFP3q7_vZRulaXd1jgp6RQI_EymMPIZbLauoBTKQq8y6cWfbS7MRMMrRIohreVf2Qbjs3iYbvKsqsdJiNysAp4ErHryNyxWSOkqCHPlgLiEgxjfIATcrU0vNR8Y5MCrZUKvcSURELGMgSTU_Jbg9C0VidF_v4Oz51z2nFBYdog27FEvraezVuZKEyg7BqtiL39f8OWglAVXvjTCxy8YCPi2kv6Im6P1iQunzgs4C8yWTnznPSnQPHE.yK0WXqSBk62Y4VFgdGIDuubsacP.2MjSR_KK5lMW2cSeVNB1eEpN77GueK0d3KgNIpz9FDEu6e9UJjHcTm4u.oiNkIiDnjuJMghGLeBgNN5iQtpGdiuBPSs_Lf.D_WbcJyImiG8a7t5VglUY..4GPBRCTtWwf.SYgjbIRtFA2JpB4O4QrFxL.0bls_RarSymZnavi1.lRgH7Vq.fQeFOePft1c6RDAZDeR5yC50XwZXub03RVTFtJ0JFldWE_1nJpKeLo9VjYz6O6aKoDh236PMOY2FSqV3qJ4Q96sfP1_737bUvS35YzeIPWaOt4V_iFRwkiLisgFPek9jTs.mJhjpddQQhj6mU.vvgK3pxjp683mG40S92CT2JLBB_E68m28RYVQL4kyIl_Qhbi3_kf9EJSp_mTpVivjoPA6vp37mdR5Cufea9crDtWHqslJmC6zUvj12FkIPVEyEUhkQKRDGbz7T.jw6lbcgenutX94FtTPfFyFCuS_r2Bf2geiwYlQXSQFexKqZlWFFdB.T_XEHWLXtCYPWd2N8JDBYFG_6LpneGpp8YjXD56bu1_wMFHlXE9OHP1jv9uJ1UTGSVjRvgo95Re.rskfVRBX6VOPKdmydTJQyEz25ibo1Z7flw8fYdVr7S5zRUghDBPjLeyRqs_T4pBIhH_C2cIMHAVHOKLTgdP_p1lFyCmoY0ScOM9GKKEaOlDSR.EgqPAKdi1Npn.q0mVd0.BnGDegVeunsurRwqi.o1yc5m.dZbpI471cEEYg.wuYYgDeltwCWPc3BMcJNEZcoe2oT50YWyqXkLi.8KqLFuSGMRCx3iNGCOhGiCrItvPzC.ly1rR6uMPvq.0ex2Ub.PJ90GZVRo6ItZPIPBfMArfn4xmQwtTzqbrFLKrZgVoNxMK3fw3YfIFZ_lDGX2WxDBNVQgI0YYIiE_fJmbGjnKmjJiqiVG4DAbYFqAstnBapOCtgGeTVM7hfiOKJQyWIvruO4dveZGoTgHbAVJG879KGC2ZJuus6crAK.LxdA_ivLqov.h6Dq62deI6tTlyaTaWwvgEUtswu792NYz_0Z1QG5QSb8IM3jADWJZu1H66EbJe_tD0MhLEM5IIS_TzuLja_q9YWcRpmT378avJdr84RReLNH9gB0Kt28fp3sMmQgQvtSDjo44xRWdOuviW_QY0JvpeAiZcODbmzSsOF4pmIEFsGXMD6uhnaIqH8Ez45AOLGBrLDVEuaCTtICquo2ds_tj6OhLKhomQ75Xt"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=91809197ed6a48d6';window._cf_chl_opt.cOgUHash = location.hash === '' && location.href.indexOf('#') !== -1 ? '#' : location.hash;window._cf_chl_opt.cOgUQuery = location.search === '' && location.href.slice(0, location.href.length - window._cf_chl_opt.cOgUHash.length).indexOf('?') !== -1 ? '?' : location.search;if (window.history && window.history.replaceState) {var ogU = location.pathname + window._cf_chl_opt.cOgUQuery + window._cf_chl_opt.cOgUHash;history.replaceState(null, null, "\/geology\/article\/31\/1\/47-50\/192515?__cf_chl_rt_tk=AfbjJxwGfIsTH97TiP48mmmoofPUsJuQGXxt051W5wI-1740579552-1.0.1.1-dgUSPkVz9I4pZzL7QPPZ.UUQDY_XMqO7HkSQQ60d8a0" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>