diff --git a/Grade 10/Science/SNC2DZ/Unit 4: Earth And Space b/Grade 10/Science/SNC2DZ/Unit 4: Earth And Space
new file mode 100644
index 0000000..fa423e9
--- /dev/null
+++ b/Grade 10/Science/SNC2DZ/Unit 4: Earth And Space	
@@ -0,0 +1,224 @@
+# Unit 4: Earth And Space
+
+`Weather`: describes the actual conditions in the atmosphere of a specifc time and space.
+    - temp, humidity, precipitation, cloud cover, pressure etc.
+
+`Climate`: 
+
+## Balance Of Energy On earth: 
+
+Em Radiation from the sun reaches the earth in many forms
+- Most harmful rays (X & UV) are absorbed and blocked by the ozone layer in the upper atmopshere
+- Visiible light, infrared and UV (some) light reaches Earth
+
+## Energy Budget Summary
+
+~ 30% is reflected back into space
+- 20% clouds
+- 10% by air & surfaces like land, water, ice and snow
+
+~70% is abosrbed
+- 50% ground (land + oceans)
+- 20% air (atmopshere + clouds)
+- Eventually, ALL 70% escapes back into space
+
+
+## Green House Effect
+
+6 Major GHGs:
+- CO2
+- Water vapour
+- Methane
+- Nitrous oxides
+- Ozone
+- CPC (chlorofluoro carbons) -> only man-made sources
+
+## Energy Transfer Within The CLimate System
+
+Major air current: The prevailing winds: west to east
+- Rising hot air at the equator & falling cool air at the poles
+- pull in nearby air to create horizontal motions from the poles to the equator
+
+Convection Current:
+- Clockwise
+- Going up drops rain (rising warm air)
+- Going down brings drought (Air cools & sinks)
+
+**Note** Due to earth's large size, the maor convection patterns are broken into 3 currents
+- Fast to slow the wind is moving faster than earth
+- Slow to fast the wind is moving slower, falling behind
+- This is called the cariolis Effect
+
+Surface Ocean Currents -> Pushed by the prevaling winds
+- Hit land: bend south/north & carry heat from equator to poles
+
+1. Warm currents 
+- reach land: warm moist air -> rain
+
+2. Cool Current: cool air
+- reach land: old dry air -> desert areas
+
+
+## Climate Change
+
+Is the global climate changing? How?
+- rising sea levels (comparaed past to now)
+- changing eco systems / ecosystems dying out due to climate change
+- avg temp in other parts of the word (compare past to now)
+- melting ice caps
+- change in migration patterns due to temp changes
+
+### Evidence Of Recent Climate Change
+- Atmospheric temp over land & water
+- Water temp
+- Size of glaciers (ancient ice)
+- amount of sea-ice & snow-cover on land
+- humidity
+
+#### Temp of Lower Atmosphere
+- fluctuates year to year but is shown to have a clear upward trend in 7 of the 10 decades since 1910
+- since 1970, global avg has increased 0.7 C above the long term avg
+- The last decade has been the warmest ever recorded
+- land heats up faster & more than water
+- more land in NH so hotter
+- some ocean regions in the antartic have cooled up to 0.8 C 
+    - melting of glaciers -> coller water
+
+#### Water Temperature
+- Have increased upward trend, recall graph
+
+#### Glacier Size
+- Avg size decreased
+
+#### Amount Of Snow & Ice Cover
+- Decreasing
+
+#### Sea Level
+- rising (thermal expansion & melting ice)
+- thermal expansion is when more heat means more energy, particles move around more and such that cover more space (more area and volume)
+
+#### Humidity
+- increases
+
+#### Other Indicators
+1. Animals disapperaring from/migrating into different territories
+    - lyme diease
+2. Earlier growth of plants in the spring
+3. changes in extreme weather (droguths, floods, hurricanes, tornados)
+
+
+## Evidence For Climate Change In The Past
+
+### Weather Records 
+
+Mostly temp & precipitation data from
+
+1. direct measurements - equipment that goes back ~ 150 years
+2. Anecdotal evicence - goes back ~2000 years (eye witness stories)
+
+Q: How do we know if the climate we're seeing is normal?
+- Older data: obtained using indirect measures of climate change ("proxy records")
+    - found in deposits of materials found in nature
+
+### Proxy Records
+
+#### Ice corrs
+- From galciers & polar ice caps
+- Provides data from ~ 800,000 years ago
+- produces a new layer every year
+- air is trapped when it froms
+    - we can directly measure volcanic activity (amount 7 type of dust trapped inside)
+    - directly meausre levels of GHG trapped
+    - accurately infer avg temp
+    - the 2 above has a realtionship, high temp = high CO2
+    
+#### Tree Rings
+- Provides data from ~10,000 years ago
+- Can infer atmopsheric temp & precipitation from thickness & annual growth rings
+    - thick ring -> warm mosit year
+    - thin ring -> cool, dry year
+
+#### Coral Reff Rings
+- provides inferred data fro 100s of years of ocean temp
+
+#### Cave rock formation 
+- growth rings provide inferred precipitation data for 25,000 - 100,000 + years
+
+#### Sedimentary rocks
+- provides fossils of plants animal pollen
+- infer temp based of type/spieces of organisms (eg tolerance range)
+- lake sediment layer thickness can infer precipitation (more rain = more sediments in lake as rain washes sediments on to the layers)
+- provides data for millions of year, but not precise
+
+#### Summary Of Past Climate Trends
+- recurring ice ages every 100,000 years for the last ~million years
+- each ice age is followed by an "interglacial" period of rapid warming, then gradual colling until the next ice age
+- last ice age was 10, 000 years a go, so the earth should be cooling
+
+## Earth's Climate
+
+### Change Of Earth's Orbit Around The Sun
+- Caused by gravity of large planets like jupiter and saturn
+- causes the ice ages
+
+### Tilt Of the Earth's Axis
+- Shifts between 22.1 to 24.5 degrees
+- currently at 23.5 and decreasing
+- happens rougly every 41, 000 years
+- More tilt Bigger seasonal differences
+- Less Titl: less seasonal differences
+    - midler winters & cooler summer promotes cooling
+
+### Precession or "wobble" of Earth's axis
+- happens every ~23,000 years
+- changes timing of seasons
+- in ~11,500 years, june will be in middle of the winder
+
+
+**Note:** Combination of alll 3 factors cause the patterns we see in the ice core temp records for the last million years
+
+**Note:** Other Factor: Continetal Drift (over the course of millions of years)
+- shfting of tectonic plates alter shape of land mass, mountinas & volcanaos
+- tem, precipitation, ocean currents changes
+
+## Short Term Change
+- Impaces climate for months/years
+
+Volcanic activity: more ash in air -> reflects more sunlight -> cooler
+
+Changes in Sun's activity: burst of extra energy by solar flares - sunspots
+
+Large glacial melts: changes direction & flow of ocean currents
+
+El Nino / La Nina: equational ocean currents normally flow west in the Pacific ocean
+- these currents reverse (En) or magnify (LN) their normal flow in a 2-7 year cycle
+- extremes can last up to 9 months
+- El Nino: causes droughts in Aisa & Australia & stroms/floods in western Americas (Reversal)
+- La Nina: causses monssons in Aisa & Austraia & droughts in western Americas (Enhancement)
+
+## Anthroprogenic Greenhouse Effect
+- Human actions that contirbute to the greenhouse effect through premature relase of GHG
+
+#### Burning Fossils fuels
+#### Deforestation 
+- carbon sink (CO2 -> wood)
+#### Agriculture
+- Cows speed up decomposition of grass and release of CO2
+- Cow farts release methane
+- food pyramid -> more meat to eat in weight than grass for same energy
+- cattle ranching, clearing large lots of land (60% of amazon for food, deforestation)
+
+#### Household use 
+- eg heating, transportation, lighting, gabage in land fills
+
+#### CO2
+- natural sources ovlcanic activity, burning organic matter, cellular respiration
+- antrhoprogenic sources: combustion of fossil fuels, deforestation
+- largest emiiter of CO2 - the oceans
+    - But they absorb more than they emit
+
+#### 
+
+
+
+