Part 9

35. What is false bedding?

36. Briefly describe the general appearance of mud-cracks and rain-prints, and say how these have been formed.

37. What is meant by a succession of strata?

38. Which kinds of stratified rocks generally have the greatest extension?

39. How do beds terminate?

40. How may planes of bedding sometimes indicate a break in the succession of strata?

41. What is the nature of joints? What are master-joints, and what is their probable cause?

42. What is cleavage, and what is its effect upon the bedding of rocks?

43. What is foliation?

44. Give examples of concretionary rocks. What is the nature of chert and flint nodules?

45. Define the terms dip and strike. What is the crop of a bed? What are anticlines and synclines?

46. What is meant by an inversion of strata?

47. How does contemporaneous erosion indicate a pause in the deposition of a series of strata?

48. What is meant by unconformability? How does unconformability prove a lapse of time between the accumulation of the underlying and overlying strata?

49. What is overlap?

50. What is a fault? What is hade? How are the strata affected on either side of a fault? What is the appearance called slickensides? Under what circumstances should we term a fault a downthrow? and when should we term it an upcast? How is the approximate age of a fault sometimes shewn?

51. What are metamorphic rocks, and what is their general appearance? In what districts of the British Islands are they most abundantly developed? What are some of the appearances relied upon for distinguishing metamorphic from igneous granite?

52. How do igneous rocks occur? Define what is meant by contemporaneous and subsequent or intrusive igneous rocks. How does a contemporaneous igneous rock affect the beds upon which it rests? What is the character of the bed overlying a contemporaneous rock? What is the general structure of a contemporaneous igneous rock? What is meant by vesicular structure? What is the general texture of a contemporaneous igneous rock? What is the nature of the jointing in igneous rocks? What is wacké?

53. What is the nature of the beds of breccia, conglomerate, ash, and tuff, with which contemporaneous igneous rocks are often associated? What is a neck of volcanic agglomerate? How are the strata affected at their junction with a 'neck'?

54. How do intrusive igneous rocks occur? How do intrusive sheets occur? What effect have they produced upon the strata above and below them? What is a dyke? What relation do they occasionally bear to sheets of igneous rock? What is a neck of intrusive igneous rock, and how have the strata surrounding it been affected?

55. Mention some of the contrasts between intrusive and contemporaneous igneous rocks. What alteration is produced upon coal with which an intrusive sheet has come in contact?

56. What are mineral veins? What is the nature of the quartz veins in granite? How are the minerals usually arranged in the great metalliferous veins? What is a pipe-vein?

57. What are the great geological agents of change?

58. What is meant by weathering? How are rocks affected at the surface in tropical countries? What chemical effect has the atmosphere on calcareous rocks? How is soil formed? How are sand dunes formed? Mention some effects of the transporting power of the atmosphere.

59. Mention some of the chemical effects of interstitial water. What is the origin of travertine or calcareous tufa?

60. How have stalactites and stalagmites been formed? Give some instances of the solvent power of springs.

61. How are caves in limestone formed? Describe some of the appearances of a country composed of calcareous rocks. Describe briefly how a river erodes its channel.

62. Describe the geological action of rain.