LAKE MEAD GEOLOGY LAS VEGAS

Jerrell Cato

History of Earth and it’s Life

Professor Lawler

What did I explore?

To my surprise there was many different rocks out in Lake Mead, I was able to find:

Lava

Sandstone

Limestone

The Landscape and life forms

I explored were:

Joshua Tree

Striped Bass and Channel Catfish

Water levels (white bands)

Joshua Tree

There are a few Joshua Tree’s in Lake Mead very easy to find when you first arrive

These trees are usually found between 3,500 – 5,000 feet

Some Joshua trees slightly resemble Palm trees

In Las Vegas it is harder for this tree water as the rainfall is quite minimal

Joshua TreePalm Tree

Striped Bass & Channel Catfish

These two fish were mainly near the boat docks and were seen in large amounts

Catfish - “Abundant in lakes and reservoirs throughout Nevada.”

The Striped Bass were more commonly seen throughout the whole lake

The Striped Bass’ were larger than the Catfish around the boat dock

Channel CatfishStriped Bass

Water Levels

Lake Mead’s water level has drastically decreased especially in the last 4 years

ear JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

20111091.73

1095.78

1096.39

1095.76

1097.90

1102.38

1107.07

1113.45

1116.04

1121.00

1125.82

1132.83

20121134.18

1133.06

1129.41

1123.93

1119.38

1115.84

1115.92

1116.56

1115.16

1116.50

1117.24

1120.36

20131122.32

1122.14

1118.59

1112.91

1108.36

1105.98

1105.92

1106.13

1106.92

1104.04

1106.36

1106.73

20141108.75

1107.94

1101.71

1094.55

1087.46

1082.66

1080.60

1081.55

1081.33

1082.79

1083.57

1087.79

20151088.51

1088.98

1084.87

1079.03

1076.57

1075.08

1078.15

1078.31

1078.10

1078.99

1078.23

1080.91

20161083.68

1084.17

1080.45

1076.13

1073.80

Water Levels

Due to the water levels decreasing in recent years it caused a bath like ring around

the rocks

The water increases by snow fall melting on the water but the amount of snow that

has been recently falling has declined

As a percentage of water from the Lake goes to Nevada and Arizona residents,

there is more going out than there is coming in from the snow.

In some places of

the lake the white

ring is as high as

130ft

Lava

Igneous rock – Formed through cooling and solidification of magma

Very small segments of lava rock was present in some areas at Lake mead,

personally It was easier to find away from the water.

Lava rock, due to the volcano differ in appearance and composition

Basalt magma often forms shield volcanoes.

Andesite magma often forms cone volcanoes.

Rhyolite magma often forms calderas. Depending on how much gas the magma

contains, it can also form cone volcanoes.

The type I found which is the most common was Basalt as the earths crust is

mainly Basalt rock

Holes in rock are

formed by gas

expansions normally

during eruptions

Sandstone

Sedimentary rock

Sandstone was the probably the most popular rock that I saw around Lake mead

as there was small and large segments

Formed by cementing particles that have eroded from pre existing rocks

Theses are very easy to identify if touching or holding as there would normally be

sand on your hand after.

Majority of the sandstone that was found near the water was broken up as the

water penetrates the rock quite easily

Sandstone can be a variety of textures and colours – the sandstone rock at Lake

Mead had more of an orange tone

Water expansion

Limestone

Sedimentary rock

These are mainly formed on the bottom of the ocean when they are rained on,

particles become compressed form limestone.

There are many grey mountains around Lake mead and these are limestone.

Limestone can be a mixture of colours including white, grey, yellow or brown

It also consists of more than50% calcium carbonate

Unconformities

A unconformity is when there may be a non-deposition, erosion or even both

It also includes sea level variations

The ages of rocks are discontinued and some people say it is time that’s missing

There are 3 types of unconformities:

Angular Unconformities

Disconformities

Nonconformities

Angular Unconformities “is an unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers”

Older rocks are buried under the younger horizontal layers of rock

when you observe an angular unconformity, you're actually observing several distinct geologic events.

Law of Superposition

The Law of Superposition stats that younger layer of rock will always be on top and

the rock below will always be older.

This law was first proposed by scientist Nicolas Steno

Archaeologists use this to determine the ages of the material they find

Older rock

Younger rock

(not the

youngest)

Other rocks and life forms at Lake Mead

Desert Spring tree

Long mouth bass

Western Grebe Long tailed brush

lizard

Pyroclastic rock

References

Lower Colorado River Operations. (n.d.). Retrieved June 15, 2016, from http://www.usbr.gov/lc/region/g4000/hourly/mead-elv.html

Lake Mead Today - Fish in Lake Mead. (n.d.). Retrieved June 15, 2016, from http://lakemeadtoday.com/fish.php

Types of volcanic rock. (n.d.). Retrieved June 15, 2016, from http://sciencelearn.org.nz/Contexts/Volcanoes/Science-Ideas-and-Concepts/Types-of-volcanic-rock

Striped Bass, general information, reproduction, habitat, food, fishing season, angling tips, handling and cooking. (n.d.). Retrieved June 15, 2016, from http://www.cptdave.com/striped-bass.html

United States. National Park Service. (n.d.). Plants. Retrieved June 15, 2016, from https://www.nps.gov/lake/learn/nature/plants.htm

United States. National Park Service. (n.d.). Low Water. Retrieved June 15, 2016, from https://www.nps.gov/lake/learn/nature/lowwater.htm

Refernces

Types of volcanic rock. (n.d.). Retrieved June 15, 2016, from

http://sciencelearn.org.nz/Contexts/Volcanoes/Science-Ideas-and-

Concepts/Types-of-volcanic-rock

Sandstone: Characteristics, Uses And Problems. (n.d.). Retrieved June 15, 2016,

from http://www.gsa.gov/portal/content/112582

(n.d.). Retrieved June 16, 2016, from http://study.com/academy/lesson/angular-

unconformity-definition-formation.html

H. (2016). Angular Unconformity. Retrieved June 16, 2016, from

https://www.youtube.com/watch?v=myzaGE2gsvA